Liquid crystal display

ABSTRACT

A liquid crystal display including a pair of substrates arranged opposite to each other, electrodes respectively formed on opposite surfaces of the pair of substrates, and an alignment regulating structural member, formed on at least one of the pair of substrates, and which includes at least one of a linear projection arranged on the electrode and a slit portion formed by removing a part of an electrode material of the electrode. A liquid crystal layer is sealed between the substrates and has a negative dielectric anisotropy, in which alignment control is made such that when a voltage is applied to the electrodes, an alignment orientation of a liquid crystal domain in a region adjacent to the alignment regulating structural member is different from an extending direction of the alignment regulating structural member by approximately 45°, and at a time of no voltage application, a liquid crystal molecule of a region where the alignment regulating structural member does not exist is substantially vertically aligned, and a liquid crystal molecule on the alignment regulating structural member or on its opposite portion is un-vertically aligned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD), andparticularly to a liquid crystal display based on an MVA (Multi-domainVertical Alignment) mode of multi-division alignment in which alignmentstates of liquid crystal molecules having a negative dielectricanisotropy are made different from each other.

2. Description of the Related Art

An LCD is regarded as the most promising substitute for a CRT amongvarious flat panel displays. It is expected that the LCD has an extendedmarket by being applied to not only a display monitor of a PC (PersonalComputer), a word processor, or an OA equipment, but also a displayportion of a consumer (household electric) appliance such as a largescreen television or a portable small-sized television.

A display operation mode of the LCD, which is most frequently used atpresent, is a normally-white mode using a TN (Twisted Nematic) liquidcrystal. This LCD includes electrodes respectively formed on oppositesurfaces of two glass substrates arranged opposite to each other, andhorizontal alignment films formed on both the electrodes. The twohorizontal alignment films are subjected to an alignment processing byrubbing or the like in the directions perpendicular to each other.Besides, polarizing plates having polarization axes adjusted to beparallel to the rubbing directions of the alignment films of the innersurfaces of the substrates are respectively arranged at the respectiveouter surfaces of the substrates.

When a nematic liquid crystal having a positive dielectric anisotropy issealed between the substrates, liquid crystal molecules in contact withthe alignment film are aligned in the rubbing direction. That is, thealignment directions of the liquid crystal molecules being in contactwith the two alignment films cross at right angles. At the same time asthat, the liquid crystal molecules between both the substrates are linedup in the direction vertical to the substrate surface while thealignment direction is successively rotated in a plane parallel to thesubstrate surface, and the liquid crystal is twisted with a twist angleof 90° between the substrates and is lined up.

If light is made incident on one of the substrate surfaces of the TNtype LCD of the above construction, when linearly polarized light havingpassed through the polarizing plate at the side of the one substratepasses through the liquid crystal layer, the polarization orientationrotates in an arc of 90° along the twist of the liquid crystalmolecules, and the light passes through the polarizing plate at the sideof the other substrate having the polarization axis orthogonal to thepolarizing plate at the side of the one substrate. By this, a brightstate display can be obtained at the time of no voltage application(normally-white mode).

When a voltage is applied between the opposite electrodes, since majoraxes of the nematic liquid crystal molecules having the positivedielectric anisotropy are aligned perpendicularly to the substratesurface, the twist disappears. The liquid crystal molecules do not havebirefringence (refractive index anisotropy) relative to the linearlypolarized light incident on the liquid crystal layer of this state.Accordingly, since the incident light does not change its polarizationdirection, it can not pass through the other polarizing plate. By this,a dark state display is obtained at the time of predetermined maximumvoltage application. When the state is again made the no voltageapplication state, it is possible to return the display to the brightstate display by alignment regulating force. Besides, a gradationdisplay becomes possible by changing the applied voltage to control thetilt of the liquid crystal molecule and to change the intensity oftransmitted light from the other polarizing plate.

An active matrix TN type TFT-LCD in which a TFT (Thin Film Transistor)is provided in each pixel as a switching element for controlling anapplied voltage between opposite electrodes for each pixel is widelyused for a PC display monitor, a portable television or the like sinceit is thin and lightweight, and a large screen and high quality can beobtained. A manufacturing technique of the TN type TFT-LCD is remarkablyadvanced in recent years, and the contrast, color reproduction propertyand the like when looking at the screen front ways are superior to aCRT. However, the TN type TFT-LCD has a fatal defect that a viewingangle is narrow. Especially, the viewing angle in the vertical directionis narrow in panel observation directions. The luminance of a dark stateincreases in one direction and an image becomes whitish, and a darkdisplay is obtained as a whole in the other direction, and a luminanceinversion phenomenon of an image occurs at a halftone. This is thebiggest defect of the TN type LCD.

As an LCD which has solved the problem of the viewing anglecharacteristics of the TN type LCD, there is an MVA-LCD disclosed inJapanese Patent No. 2947350. An example of the construction of theMVA-LCD will be described. First, electrodes are respectively formed atthe sides of opposite surfaces of two substrates having a predeterminedgap and arranged opposite to each other. Vertical alignment films areformed on both the electrodes, and a liquid crystal having a negativedielectric anisotropy is sealed between the two vertical alignmentfilms. A plurality of linear projections made of insulators areperiodically formed between the electrodes and the vertical alignmentfilms of both the substrates. The linear projections opposite to eachother between the two substrates are arranged while they are shifted bya half pitch from each other when viewed from the substrate surface. Thelinear projections are used for alignment control to divide the liquidcrystal in a pixel region into plural alignment orientations.Incidentally, even if slit portions are provided on the electrodesinstead of the linear projections, the alignment division can becontrolled.

Two polarizing plates having polarization axes orthogonal to each otherare provided at the outer surfaces of the two substrates. The attachmentdirections of the polarizing plates are adjusted so that theorientations of the major axes of the liquid crystal molecules tilted onthe substrate display surfaces at the time of voltage application becomeapproximately 45° with respect to the polarization axes of thepolarizing plates when viewed from the substrate surface.

When a nematic liquid crystal having a negative dielectric anisotropy issealed between the substrates, the major axes of the liquid crystalmolecules are aligned in the vertical direction with respect to the filmsurface of the vertical orientation film. Thus, the liquid crystalmolecules on the substrate surface are aligned vertically to thesubstrate surface, and the liquid crystal molecules on the tiltedsurfaces of the linear projections are aligned obliquely to thesubstrate surface.

When light is made incident on one of the substrate surfaces in thestate where a voltage is not applied between both the electrodes of theMVA-LCD of the above construction, the linearly polarized light havingpassed through the one polarizing plate and incident on the liquidcrystal layer travels in the directions of the major axes of thevertically aligned liquid crystal molecules. Since birefringence doesnot occur in the directions of the major axes of the liquid crystalmolecules, the incident light travels without changing the polarizationorientation, and is absorbed by the other polarizing plate having thepolarization axis orthogonal to that of the one polarizing plate. Bythis, a dark state display is obtained at the time of no voltageapplication (normally-black mode).

When a voltage is applied between the opposite electrodes, the majoraxes of the liquid crystal molecules are aligned parallel to thesubstrate surface while the alignment orientations of the liquid crystalmolecules on the substrate surface are regulated in accordance with thealignment orientations of the liquid crystal molecules tilted by thelinear projections in advance.

The liquid crystal molecule has birefringence relative to the linearlypolarized light incident on the liquid crystal layer of this state, andthe polarization state of the incident light is changed according to thetilt of the liquid crystal molecule. At the time of predeterminedmaximum voltage application, since the light passing through the liquidcrystal layer becomes, for example, linearly polarized light in whichthe polarization orientation rotates in an arc of 90°, it passes throughthe other polarizing plate and a bright state display is obtained. Whenthe state of no voltage application is again produced, the display canbe returned to the dark state display by the alignment regulating force.Besides, a gradation display becomes possible by changing the appliedvoltage to control the tilt of the liquid crystal molecule and to changethe intensity of transmitted light from the other polarizing plate.

According to the active matrix MVA system TFT-LCD in which a TFT isformed in each pixel, since the alignment orientation of the liquidcrystal in the pixel can be divided into plural ones, as compared withthe TN type TFT-LCD, an extremely wide viewing angle and high contrastcan be realized. Besides, since a rubbing processing is not required,the manufacturing process becomes easy and the manufacturing yield canbe improved.

However, the conventional MVA system TFT-LCD can be improved in theresponse time of a display. That is, a high speed response can be madein the case where black is again displayed after a black display waschanged to a white display. However, a response time when a halftone isdisplayed from another halftone is rather inferior to the TN typeTFT-LCD.

Besides, also with respect to the transmittance of light, although theconventional MVA system TFT-LCD is substantially twice as excellent as awide viewing angle LCD of an IPS (In-plane Switching) system of ahorizontal electric field system, it is inferior to the TN type TFT-LCD.

As stated above, although the MVA system TFT-LCD has solved the problemof the conventional LCD with respect to the viewing angle, contrast, andresponse time of black-white-black display, it does not exceed theconventional TN type LCD with respect to the response time at a halftonedisplay and the transmittance.

Here, the reason why the halftone response of the conventional MVA-LCDis slower than the conventional TN type LCD will be described withreference to FIGS. 73A to 74C. FIGS. 73A to 73C show a schematicconstruction of a section obtained by cutting an MVA-LCD panel in thedirection vertical to a substrate surface. FIG. 73A shows an alignmentstate of liquid crystal at the time of no voltage application, and FIG.73B shows an alignment state of the liquid crystal at the time ofvoltage application. FIG. 73C is a conceptual view showing an alignmentcontrol state. FIGS. 74A to 74C show a schematic construction of asection obtained by cutting a TN type LCD panel in the directionvertical to a substrate surface. FIG. 74A shows an alignment state ofliquid crystal at the time of no voltage application, and FIG. 74B showsan alignment state of the liquid crystal at the time of voltageapplication. FIG. 74C is a conceptual view showing an alignment controlstate.

First, a TN type LCD 100 will be described with reference to FIGS. 74Ato 74C. As shown in FIG. 74A, at the time of no voltage application, aliquid crystal 102 of the TN type LCD 100 is twisted with a twist angleof 90° and is aligned between an electrode 108 at the side of an uppersubstrate 104 and an electrode 110 (either alignment film is not shown)at the side of a lower substrate 106 arranged opposite to each other.When a voltage is applied between the electrodes 108 and 110, as shownin FIG. 74B, liquid crystal molecules rise almost vertically to thesurfaces of the substrates 104 and 106 and the twist disappears. If thevoltage application is removed, the liquid crystal molecules rotate inthe direction substantially parallel to the original surfaces of thesubstrates 104 and 106 and return to the twist alignment. As statedabove, in the case of the TN type LCD 100, as shown by an oblique lineportion 112 of FIG. 74C, we can consider that not only the liquidcrystal molecules in the vicinity of the interfaces of the not-shownalignment films on the electrodes 108 and 110 are alignment-controlledby the regulating forces of the alignment films, but also the liquidcrystal molecules in the center region of the liquid crystal layer 102are also alignment-controlled to a certain degree by a twist alignmentdue to addition of a chiral agent or the like.

On the other hand, as shown in FIG. 73A, at the time of no voltageapplication, in a liquid crystal 124 of an MVA-LCD 114, liquid crystalmolecules other than those in the vicinity of linear projections 126,128, and 130 are almost vertically aligned between an electrode 120 atthe side of an upper substrate 116 and an electrode 122 (eitheralignment film is not shown) at the side of a lower substrate 118arranged opposite to each other. The liquid crystal molecules in thevicinity of the linear projections 126 to 130 are aligned almostvertically to the surfaces of the not-shown alignment films on theoblique surfaces of the projections and are tilted with respect to thesubstrate surfaces. When a voltage is applied between the electrodes 120and 122, as shown in FIG. 73B, the tilt of the liquid crystal issuccessively propagated in the tilt directions of the liquid crystalmolecules in the vicinity of the linear projections 126 to 130 foralignment regulation. Thus, a time lag occurs until the liquid crystalin a portion between a linear projection and an adjacent linearprojection, that is, in the center of the gap portion finishes tilting.Especially, in the gradation change from black to a dark halftone, thechange amount of applied voltage is small and the change of theintensity of an electric field in the liquid crystal is small, so thatthe propagation speed of the tilt of the liquid crystal molecule islowered.

Falling directions of the liquid crystal molecules existing in the spaceportions of the linear projections 126 to 130 are not determined if thetilt direction is not propagated from the linear projections 126 to 130.That is, as shown by oblique line portions 132 of FIG. 73C, thealignment of the liquid crystal in the MVA-LCD is regulated by only thedistortion of an electric field in the vicinity of the interfaces of thealignment films to which the regulating forces of the alignment films onthe substrate surfaces reach, and at the alignment films on the linearprojections 126 to 130 and their vicinity, and the liquid crystalalignment of the other region is only indirectly controlled.

Even in the conventional MVA construction, if the space distance (pitch)of the linear projections of the upper and lower substrates is madeshort, the response time can be made short. However, as described above,in a general MVA-LCD, since the tilt orientation of liquid crystal isdetermined by the projection oblique surface of an insulator, the tiltportion must have a certain degree of width, length and height. Thus,the pitch of the upper and lower projections cannot be made very short.

FIG. 75 shows an alignment state of liquid crystal molecules at the timeof voltage application when the MVA-LCD shown in FIGS. 73A to 73C isviewed from the side of the lower substrate 118. Among the three linearprojections 126, 128 and 130 extending horizontally in the drawing, theupper and lower two projections 126 and 128 are formed on the lowersubstrate 118, and the center one projection 130 is formed on the uppersubstrate 116.

The liquid crystal molecules, which are aligned substantially verticallyto the substrates 116 and 118 at the time of no voltage application, arealignment-divided, as shown in FIG. 75, at the time of voltageapplication into an alignment region A in which they are aligned in thedirection (upward direction of the paper plane) toward the linearprojection 128 at the side of the lower substrate 118 from the linearprojection 130 at the side of the upper substrate 116, and an alignmentregion B in which they are aligned in the direction (downward directionof the paper plane) toward the linear projection 126 at the side of thelower substrate 118 from the linear projection 130.

That is, at the time of voltage application, the liquid crystalmolecules over the adjacent alignment regions A and B at both sides ofthe linear projection 130 are alignment-divided so that the orientationof the major axis of the liquid crystal of the alignment region Abecomes substantially +90° with respect to the extending direction ofthe linear projection 130, and the orientation of the major axis of theliquid crystal of the alignment region B becomes substantially −90° withrespect to the extending direction of the linear projection 130. On theother hand, at the time of voltage application, the liquid crystalmolecules in the vicinity of tops of the linear projections 126 to 130are tilted in the directions in which the respective projections extend,and they are aligned so that the alignment orientation becomessubstantially 0° or 180° (parallel) with respect to the extendingdirections of the respective linear projections 126, 128 and 130.

As stated above, at the time of voltage application, with respect to thealignment orientations (substantially 0° or 180° with respect to theextending directions of the linear projections 126 to 130) of the liquidcrystal molecules in the vicinity of the tops of the linear projections126, 128 and 130, the alignment orientations of the liquid crystalmolecules of the display region on the substrates 116 and 118 come tohave a state in which they rotate in an arc of 90°. Thus, as shown inFIG. 75, the liquid crystal molecules aligned in the orientation of 45°with respect to the extending directions of the respective linearprojections 126, 128 and 130 are arranged at both sides of the tiltsurfaces of the linear projections 126 to 130. However, polarizationaxes P and A of polarizing plates indicated by orthogonal arrows in thedrawing are arranged to be tilted with an angle of 45° with respect tothe alignment orientations of the liquid crystal molecules of thedisplay regions A and B on the substrates 116 and 118.

Accordingly, since the alignment orientations of the liquid crystalmolecules aligned in the orientation of 45° with respect to therespective linear projections 126, 128 and 130 become parallel to andorthogonal to the polarization orientations of the polarization axes Pand A of the polarizing plates, as shown by broken lines in the drawing,two dark lines (discrimination lines) 140 and 142 are generated at bothsides of the tilt surfaces of the linear projections 126 to 130.Incidentally, the two dark lines 140 and 142 are formed for everyinterval between a first singular point (indicated by (+1) in thedrawing) and a second singular point (indicated by (−1) in the drawing)of alignment vector fields formed on the linear projections 126 to 130.At the first singular point (+1), the orientations of the major axes ofthe liquid crystal molecules are directed toward substantially the samepoint, and at the second singularity point (−1), part of the liquidcrystal molecules are directed in different directions.

In the conventional MVA-LCD like this, if an attempt to shorten theresponse time of a halftone is made by shortening the pitch of the upperand lower projections to increase the formation density, not only theoccupied area of the projections in the pixel region is increased, butalso the formation density of the two dark lines 140 and 142 formed atboth sides of the projection is also increased, and a drop intransmittance becomes so large that it can not be neglected.Accordingly, there arises a problem that if the formation density of thelinear projections is made high in order to improve the responsecharacteristics of the liquid crystal, the transmittance is lowered. Asstated above, the conventional MVA-LCD construction has a problem thatthe improvement of the response characteristics of the liquid crystaland the improvement of the transmittance have a trade-off relation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a liquid crystaldisplay in which a drop in transmittance is suppressed and responsecharacteristics are improved.

Another object of the present invention is to provide a liquid crystaldisplay in which a drop in response characteristics is suppressed andtransmittance is improved.

The above objects are achieved by a liquid crystal display characterizedby comprising a pair of substrates having a predetermined cell gap andarranged opposite to each other, vertical alignment films formed betweenthe pair of substrates, a liquid crystal layer sealed between thevertical alignment films and having a negative dielectric anisotropy, analignment regulating structural member arranged at least one of the pairof substrates, for regulating a total alignment direction of liquidcrystal molecules in the liquid crystal layer at a time of voltageapplication, and a cured material provided in the liquid crystal layerand including a liquid crystal skeleton for tilting the liquid crystalmolecules.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are views showing the operation principle of a liquidcrystal display according to a first embodiment of the presentinvention;

FIG. 2 is a view showing application effects of example 1-1 according tothe first embodiment of the present invention;

FIG. 3 is a view showing the measurement results of response speedaccording to the example 1-1 of the first embodiment of the presentinvention;

FIG. 4 is a view showing the measurement results of response speedaccording to comparative example 1-1;

FIG. 5 is a view showing the relation between the tilt angle of liquidcrystal molecules on an alignment regulating structural member andtransmittance (indicated by applied voltage) before formation ofpolymer;

FIGS. 6A and 6B are views showing the schematic construction of an MVAcell according to example 1-3 of the first embodiment of the presentinvention;

FIG. 7 is a view showing the schematic construction of an MVA cellaccording to example 1-4 of the first embodiment of the presentinvention;

FIGS. 8A to 8D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 9A to 9D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 10A to 10D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 11A to 11D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 12A to 12D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 13A to 13D are views showing the alignment state of liquid crystalmolecules with respect to an alignment regulating structural member or asingular point control portion;

FIGS. 14A and 14B are views showing a state in which a liquid crystalpanel including a cruciform projection structural member 4 formed on onesubstrate 1 is viewed in the direction of a normal of a substratesurface;

FIG. 15 is a view showing a state in which a liquid crystal panelaccording to example 2-1 of a second embodiment of the present inventionis viewed in the direction of a normal of a substrate surface;

FIG. 16 is a graph for comparing the liquid crystal panel of the example2-1 in the second embodiment of the present invention with a liquidcrystal panel of a comparative example;

FIG. 17 is a view showing a state in which a liquid crystal panelaccording to example 2-2 of the second embodiment of the presentinvention is viewed in the direction of a normal of a substrate surface;

FIG. 18 is a graph for comparing the liquid crystal panel of the example2-2 in the second embodiment of the present invention with a liquidcrystal panel of a comparative example;

FIG. 19 is a sectional view showing the construction of a liquid crystalpanel according to a third embodiment of the present invention;

FIGS. 20A to 20D are views for explaining a manufacturing method of theliquid crystal panel according to the third embodiment of the presentinvention;

FIG. 21 is a view showing another example of the construction of theliquid crystal panel according to the third embodiment of the presentinvention and a state in which two adjacent liquid crystal cells areviewed against a substrate surface;

FIG. 22 is a view showing still another example of the construction ofthe liquid crystal panel according to the third embodiment of thepresent invention and a comparative example, and a state in which twopixels of the liquid crystal panel are viewed in the direction of anormal of a substrate surface;

FIG. 23 is a view for explaining a problem to be solved by a fourthembodiment of the present invention;

FIG. 24 is a view for explaining a problem to be solved by the fourthembodiment of the present invention;

FIG. 25 is a view showing a liquid crystal display according to example4-1 of the fourth embodiment of the present invention;

FIG. 26 is a view showing the liquid crystal display according to theexample 4-1 of the fourth embodiment of the present invention;

FIG. 27 is a view schematically showing a section of an MVA cellaccording to the example 4-1 of the fourth embodiment of the presentinvention;

FIG. 28 is a view schematically showing the section of the MVA cellaccording to the example 4-1 of the fourth embodiment of the presentinvention;

FIG. 29 is a view schematically showing a section of a MVA cellaccording to a comparative example of the example 4-1 of the fourthembodiment of the present invention;

FIG. 30 is a view schematically showing the section of the MVA cellaccording to the comparative example of the example 4-1 of the fourthembodiment of the present invention;

FIG. 31 is a view showing a liquid crystal display according to example4-2 of the fourth embodiment of the present invention;

FIG. 32 is a view schematically showing a section of an MVA cellaccording to the example 4-2 of the fourth embodiment of the presentinvention;

FIG. 33 is a view schematically showing the section of the MVA cellaccording to the example 4-2 of the fourth embodiment of the presentinvention;

FIG. 34 is a view showing a liquid crystal display according to example4-3 of the fourth embodiment of the present invention;

FIG. 35 is a view showing a liquid crystal display according to example5-1 of a fifth embodiment of the present invention;

FIG. 36 is a view showing the liquid crystal display according to theexample 5-1 of the fifth embodiment of the present invention;

FIG. 37 is a view showing a liquid crystal display according to example5-2 of the fifth embodiment of the present invention;

FIGS. 38A and 38B are views showing a liquid crystal panel constructionaccording to example 6-1 of a sixth embodiment of the present invention;

FIGS. 39A and 39B are views showing a liquid crystal panel constructionaccording to example 6-2 of the sixth embodiment of the presentinvention;

FIGS. 40A and 40B are views showing a liquid crystal panel constructionaccording to example 6-3 of the sixth embodiment of the presentinvention;

FIG. 41 is a view showing a liquid crystal panel construction accordingto example 6-4 of the sixth embodiment of the present invention;

FIG. 42 is a view showing a liquid crystal panel construction accordingto example 6-5 of the sixth embodiment of the present invention;

FIG. 43 is a view showing a liquid crystal panel construction accordingto example 6-6 of the sixth embodiment of the present invention;

FIG. 44 is a view for explaining a problem to be solved by a seventhembodiment of the present invention;

FIGS. 45A to 45F are views for explaining the problem to be solved bythe seventh embodiment of the present invention;

FIGS. 46A to 46H are views for explaining the problem to be solved bythe seventh embodiment of the present invention;

FIGS. 47A to 47F are views for explaining the problem to be solved bythe seventh embodiment of the present invention;

FIGS. 48A and 48B are views showing a liquid crystal panel constructionaccording to example 7-1 of the seventh embodiment of the presentinvention;

FIGS. 49A and 49B are views showing measurement results of responsespeed of the liquid crystal panel according to the example 7-1 of theseventh embodiment of the present invention;

FIGS. 50A and 50B are views showing a liquid crystal panel constructionaccording to example 7-2 of the seventh embodiment of the presentinvention;

FIGS. 51A and 51B are views showing a liquid crystal panel constructionaccording to example 7-3 of the seventh embodiment of the presentinvention;

FIGS. 52A and 52B are views showing a liquid crystal panel constructionaccording to example 7-4 of the seventh embodiment of the presentinvention;

FIG. 53 is a view for explaining a manufacturing method of a liquidcrystal panel according to example 7-5 of the seventh embodiment of thepresent invention;

FIG. 54 is a view showing a liquid crystal panel construction accordingto example 7-6 of the seventh embodiment of the present invention;

FIG. 55 is a view for explaining a problem to be solved by an eighthembodiment of the present invention;

FIG. 56 is a view for explaining the problem to be solved by the eighthembodiment of the present invention;

FIG. 57 is a view showing the dependency of response characteristics ofa liquid crystal display on a cell gap (cell thickness) in the eighthembodiment of the present invention;

FIG. 58 is a view showing the relation between a height of a bank of aliquid crystal display and a contrast ratio in the eighth embodiment ofthe present invention;

FIG. 59 is a view showing the space width (pitch) dependency of responsecharacteristics of the liquid crystal display in the eighth embodimentof the present invention;

FIG. 60 is a view showing the space width (pitch) dependency of responsecharacteristics of the liquid crystal display in the eighth embodimentof the present invention;

FIG. 61 is a view showing the space width (pitch) dependency of responsecharacteristics of the liquid crystal display in the eighth embodimentof the present invention;

FIG. 62 is a view showing the relation between bank width and paneltransmittance in the eighth embodiment of the present invention;

FIG. 63 is a view for explaining a problem to be solved by a ninthembodiment of the present invention;

FIG. 64 is a view for explaining the problem to be solved by the ninthembodiment of the present invention;

FIG. 65 is a view for explaining the problem to be solved by the ninthembodiment of the present invention;

FIG. 66 is a view showing the parameter dependency of an on stateresponse time in a VA system LCD in the ninth embodiment of the presentinvention;

FIG. 67 is a view showing the response characteristics of a VA systemLCD using a liquid crystal shown in Table 11 in the ninth embodiment ofthe present invention;

FIG. 68 is a view showing a sectional construction of an MVA-LCD in theninth embodiment of the present invention;

FIG. 69 is a view showing the propagation state of the tilt of liquidcrystal molecules in the MVA-LCD in the ninth embodiment of the presentinvention;

FIG. 70 is a view showing the parameter dependency of an on stateresponse time in the MVA-LCD in the ninth embodiment of the presentinvention;

FIG. 71 is a view showing a sectional construction of the MVA-LCD in theninth embodiment of the present invention;

FIGS. 72A to 72D are views showing results of microscopic observation oftransient response characteristics of the MVA-LCD in which a space s ischanged in the ninth embodiment of the present invention;

FIGS. 73A to 73C are views for explaining the reason why a halftoneresponse of a conventional MVA-LCD is slow as compared with aconventional TN type LCD;

FIGS. 74A to 74C are views for explaining the reason why the halftoneresponse of the conventional MVA-LCD is slow as compared with theconventional TN type LCD; and

FIG. 75 is a view showing an alignment state of liquid crystal moleculesat the time of voltage application when the MVA-LCD shown in FIGS. 73Ato 73C is viewed from the side of a lower substrate 118.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A liquid crystal display according to a first embodiment of the presentinvention will be described with reference to FIGS. 1A to 7. Thisembodiment is characterized in that in a liquid crystal display forregulating the alignment of all liquid crystal molecules at the time ofvoltage application by local alignment regulation, as typified by theabove MVA system, a propagation process of a tilt of the liquid crystalmolecule at the time of a response operation by voltage application iseliminated, and the whole display region is tilted at the same time. Inaddition, there is provided a liquid crystal display showing veryhigh-speed response characteristics in all gradations by improving theresponse property itself of the liquid crystal molecules to an electricfield.

In order to improve the response speed in the MVA system or the like, itis indispensable that a time required for tilt propagation of liquidcrystal molecules is made zero and the whole surface of a display regionis made to tilt at the same time. In order to realize the whole surfacesimultaneous tilt, it is effective to form a stable state in which inthe state of no voltage application, liquid crystal molecules areslightly tilted with respect to a substrate interface over the wholesurface.

The operation principle of this embodiment is shown in FIGS. 1A and 1B.As a result of earnest trial, it has been found that the great speed-upin the response speed by the whole surface simultaneous tilt can berealized by forming, as shown in FIG. 1A, a photo-cured material of aphoto-curable composition having a liquid crystal skeleton in a liquidcrystal layer, and by forming the liquid crystal skeleton in a statewhere it is tilted with respect to a substrate. As shown in FIG. 1B, theliquid crystal skeleton is fixed at an angle different from an alignmentcontrol direction by an alignment film, and by adsorption power betweenthe liquid crystal skeleton and liquid crystal molecules, the liquidcrystal molecules are tilted toward the side of the alignment directionof the liquid crystal skeleton rather than the alignment controldirection by the alignment film over the whole surface.

The magnitude of this tilt can be arbitrarily changed by a ratio of theliquid crystal skeleton to an amount of liquid crystal, and thealignment direction of the liquid crystal skeleton. Besides, at thistime, since an attractive force toward the alignment direction of theliquid crystal skeleton exists for the liquid crystal molecules of thewhole including the bulk, it becomes possible to realize higher speedswitching than a state where a tilt alignment is caused only in thevicinity of the interface by rubbing or the like.

This function can also be realized to some degree by high polymermolecules having no liquid crystal skeleton. However, in order to fixthe liquid crystal molecules uniformly in a panel without disturbing thealignment state of the liquid crystal molecules and by an additionamount of several wt %, a material showing a liquid crystal propertybefore hardening is desirable. The material is easily mixed in a liquidcrystal as a host and can be uniformly distributed, and structureformation at the time of hardening hardly disturbs the alignment of theliquid crystal molecules, so that an excellent fixing state can beobtained.

The alignment fixing technique of liquid crystal using such a highmolecular material can also be applied to other existing operationsystems (operation modes) in addition to the MVA system. However, it hasbeen found that operation modes in which a great effect can be obtainedby applying the alignment fixing technique in this embodiment arelimited.

FIG. 2 shows main improvement effects of respective operation modes byalignment fixing using a high molecular material. As shown in FIG. 2, inthe respective modes of a TN type, an a-TN type, an ECB type and an IPStype, the improvement effect of response speed at the time of voltageapplication can be obtained by applying this embodiment. However, in theTN type and the a-TN type, a drop in optical rotatory power and a dropin contrast are caused.

Besides, in the TN type, the a-TN type, the ECB type, and the IPS type,except for the a-TN type, it is necessary to perform an alignmentprocessing in any modes. The alignment regulating power of the liquidcrystal molecules by this interface alignment processing is very high,and controllability of a tilt angle or the like is also very excellent.However, one step is added to panel manufacturing steps by thisinterface alignment processing, and in addition, a polymer structureformation process is added in order to realize alignment stabilizationusing the high molecular material of this embodiment. Besides, in ahorizontal alignment mode using a nematic liquid crystal, especially inan operation mode in which the time of a horizontal alignment is madeblack, a slight disturbance of the alignment order of the liquid crystalmolecules or a change of a tilt greatly influences the display quality.In view of the above, it is conceivable that even if this embodiment isapplied to the TN type, the ECB type, and the IPS type, there are fewmerits.

Although the OCB mode has features that a high speed response and a wideviewing angle can be obtained, there is a defect that a high drivingvoltage is required to form a bend alignment, and when the power supplyis again switched on after the power supply is cut, re-alignment must bemade. Since the alignment stabilization by the high molecular materialcan fix the bend alignment, this defect can be improved. However, forthat purpose, it is necessary to add the high molecular material at ahigh concentration, and as a result, scattering of transmitted lightoccurs and transmittance is lowered. Besides, the degree of freedom ofliquid crystal molecules in the space is lowered, and the response speedis lowered.

In the FLC, although a high speed operation about 1000 times as fast asthe nematic liquid crystal is possible, since it has bistability, thereis a defect that a halftone display is difficult to produce. Besides,since a chevron layer construction is adopted in a normally used SmC*layer, there is also a problem that a zigzag alignment defect is apt tooccur. These can be improved by using the mutual action to the liquidcrystal skeleton in the high molecule. However, the tilt angle isdecreased by the mutual action, and a drop in response speed is alsocaused. Besides, there also arises a problem that a uniform alignmentbecomes difficult to obtain in the FLC in which alignment control isdifficult from the first.

Differently from the operation modes described above, in the verticalalignment type ASM and the MVA mode, the tilt direction is regulated byan alignment regulating structural member locally provided on thesurface of the substrate. Thus, an interface alignment processingprocess such as rubbing is unnecessary. Besides, a vertical alignment ispurely made from the interface to the bulk in the state of no voltageapplication and a black display is produced. Thus, as compared with theother horizontal modes such as the TN mode, even if the alignment orderis disturbed by forming the polymer structure according to thisembodiment, a drop in contrast by the change of refractive indexanisotropy is very low.

However, differently from the MVA mode, in the ASM mode, when tiltingoccurs in the substrate surface direction in any divided displayregions, a twisted alignment state of about 90° is produced betweenupper and lower substrates. Thus, differently from the MVA mode,similarly to the foregoing TN mode, there is a problem that the twiststate is disturbed at the time of alignment stabilization. Accordingly,there are many restrictions in the addition amount and the tilt anglegiven to the bulk, and it is difficult to obtain the effect of highmolecule stabilization to the utmost. Besides, the twist deformationoccurs at the time of tilting, which prevents a high-speed response.

From the above, when the alignment stabilization technique by thephoto-cured material is applied to the MVA mode satisfying the followingconditions, the maximum effect can be first obtained.

1. The tilt directions of all liquid crystal molecules are regulated byan alignment regulating structural member locally provided on thesubstrate surface, and the response operation is performed by thepropagation of the tilt of the liquid crystal molecules; and

2. they are formed of the nematic phase, there is no twist deformation,and tilting simply occurs in the uniaxial direction to the substratesurface direction.

In the case where the alignment regulating structural member is a linearprojection as in the MVA mode, the liquid crystal molecules on thealignment regulating structural member are tilted along the extendingdirection of the linear projection. A place where the tilt directions ofthe liquid crystal molecules on the projection are different by 180°which is azimuth angle in the projection extending direction becomes asingular point of the alignment. In the case where the liquid crystalmolecules in each domain are tilted in the vertical direction to theextending direction of the alignment regulating structural member, asshown in FIG. 75, if the influence of the singular point is high, thealignment direction of the display region is shifted in the extendingdirection of the alignment regulating structural member. If thephoto-curing material is cured in such a state, the polymer structure isformed to be superimposed on the disturbance of the alignment, thecontrast is lowered and the roughness of a display occurs.

In order to solve this, first, the photo-curing material is cured insuch a way that the tilt angle of the liquid crystal molecule on thealignment regulating structural member is small, and the deformationoccurring between the liquid crystal molecule on the alignmentregulating structural member and the liquid crystal molecule of a spaceportion is made a spray deformation shifted in a polar angle direction.That is, when the tilt angle of the liquid crystal molecule on thealignment regulating structural member is made θ_(pr), which is the tiltangle of the LC molecule from the vertical state, as shown in FIG. 1Bwhen the photo-curing material is cured in the state satisfying0°≦θ_(pr)<45°, an excellent alignment state can be obtained.

Second, the tilt direction of the liquid crystal molecule on thealignment regulating structural member is always made a constantdirection and the generation of a singular point is suppressed. That is,if a construction is such that an angle between orientation angledirections at the time of tilting of liquid crystal molecules in regionsdivided by the alignment regulating structural member as a boundary doesnot become 180°, the alignment direction is regulated in one directionstable in energy, and the generation of the singularly point to disturbthe alignment direction of the space portion is suppressed. At thistime, it is desirable that the angle between the orientation angledirections at the time of tilting of the liquid crystal molecules in theregions is 90° in view of transmittance.

Third, it is appropriate that an auxiliary alignment control factor tosuppress the disturbance of the orientation angle direction at the timeof tilting is added in addition to the alignment regulating structuralmember for roughly regulating the tilt direction (propagation direction)of a display region. In the conventional MVA system, for example, aplurality of linear projections are arranged in parallel to one another,and the liquid crystal molecules of a space portion between theprojections are tilted in the direction perpendicular to the extendingdirection of the projections by the propagation of the tilt.Accordingly, a singular point is generated, and the tilt state ispropagated while the orientation angle in the vicinity of the projectionedge is shifted. Accordingly, if the alignment control factor toregulate the orientation angle in the direction perpendicular to theextending direction is auxiliary provided in the space portion betweenthe projections, an excellent alignment state can be obtained in thedisplay region without being influenced by the alignment state on thealignment regulating structural member.

By using this embodiment, the propagation process of the tilt of theliquid crystal molecules at the time of the response operation iseliminated and the whole display region can be simultaneously tilted.Besides, the response property of the liquid crystal molecule withrespect to an electric field can also be improved. Especially, in theliquid crystal display in which an alignment processing such as rubbingis not performed to the alignment film and the total alignment of theliquid crystal molecules at the time of voltage application is regulatedby the locally provided alignment regulating structural member, veryhigh speed response characteristics can be realized.

Hereinafter, specific examples will be described.

EXAMPLE 1-1

Liquid crystal monoacrylate monomer UCL-001-K1 of 2.5 wt % of DainipponInk Co., Ltd was added to liquid crystal material A having a negativedielectric anisotropy, and after being injected into an MVA cell, it wascured by ultraviolet rays while a voltage of 5.0 V was applied. Here,polyamic-acid material X was used as a vertical alignment film, banks(projections) each having a height of 1.5 μm and a width of 10 μm arealternately provided with resist LC-200 of Shipley Co., Ltd to make aspace of 37.5 μm, and a cell gap was made 4.0 μm. A driving mode isnormally-black.

FIG. 3 shows measurement results of response speed in this example. Thehorizontal axis indicates the transmittance (%) obtained when apredetermined voltage is applied from an applied voltage of 0 V, and thevertical axis indicates the response speed (ms; millisecond). Apolygonal line α indicates a case where a photo-curing material is notadded in the liquid crystal, and a polygonal line β indicates a casewhere the photo-curing material of 2.5 wt % is added as mentioned above.As compared with the cell in which the photo-curing material is notadded, an improvement greatly exceeding double is obtained. Whentransmittance in a dark state was measured by a luminance meter LCD-7000of Otsuka Denshi Co., Ltd., it was 0.017%, and the value almost equal tothe case where the photo-curing material was not added was obtained.

COMPARATIVE EXAMPLE 1-1

Liquid crystal monoacrylate monomer UCL-001-K1 of 2.5 wt % of DainipponInk Co., Ltd was added to liquid crystal material P having a positivedielectric anisotropy, and after being injected into a TN liquid crystalcell, it was cured by ultraviolet rays while a voltage of 5.0 V wasapplied. Here, polyimide homogenous alignment film material Z was usedfor an alignment film, and a rubbing processing was performed as analignment processing to upper and lower substrates. A driving mode isnormally-white. A cell gap was made 4.0 μm. At this time, similarly tothe example 1-1, when transmittance in a dark state was measured by aluminance meter LCD-7000 of Otsuka Denshi Co., Ltd., it was 0.41%, thatis, the transmittance twenty or more times as high as that of the cellshown in the example 1-1 was observed. In order to make thetransmittance in the dark state 0.1% or less, it was necessary to causecuring by application of about 2 V.

FIG. 4 shows measurement results of response speed in this comparativeexample. The horizontal axis indicates the applied voltage (V), and thevertical axis indicates the response speed (ms). A polygonal line αindicates a case where a photo-curing material is not added in theliquid crystal, and a polygonal line β indicates a case where thephoto-curing material of 2.5 wt % is added as mentioned above. Animprovement in response speed was about 20 percent, and was considerablylow as compared with the example 1-1.

EXAMPLE 1-2

In the MVA cell of the example 1-1, when the alignment state at the timeof voltage application of 5.0 V was observed, disturbance of alignmentcaused by singular points generated on the alignment regulatingstructural members as shown in FIG. 75 was observed in the space portionbetween the alignment regulating structural members. When the change ofthe alignment state with respect to the applied voltage at the time ofphoto-curing was examined, an excellent alignment was obtained tillapplication of 3V, and the disturbance of the alignment becamenoticeable from the time of application of 3.5 V.

Next, the alignment film material was changed to a polyamic-acidmaterial whose vertical alignment ability is much stronger than that ofvertical alignment film material X. and when a similar experiment wascarried out, an excellent alignment was obtained till application of 3.5V.

FIG. 5 shows the relation between the tilt angle of liquid crystalmolecules on the alignment regulating structural members and the appliedvoltage before polymer formation in these cells. The horizontal axisindicates the applied voltage (V), and the vertical axis indicates thetilt angle (deg). The tilt angle θ_(pr) of 90° is the value when themaximum transmittance is got on the alignment regulating structuralmember using vertical alignment film material X. In the drawing, apolygonal line α indicates a case where the alignment film is made ofvertical alignment film material X and a polygonal line β indicates acase where the alignment film is made of vertical alignment filmmaterial Y. As is apparent from FIG. 5, it has been confirmed that aboundary as to whether or not the disturbance of alignment is producedis about a tilt angle θ_(pr) of 45°.

EXAMPLE 1-3

FIGS. 6A and 6B show a schematic construction of an MVA cell accordingto the example. FIG. 6A shows a state where the cell is viewed against asubstrate surface, and FIG. 6B shows a section taken along line A-A ofFIG. 6A. The MVA cell of this example has the construction in whichauxiliary alignment control factors 5 for suppressing the disturbance oforientation angle direction at the time of tilting are added in additionto alignment regulating structural members 4 and 6 for roughlyregulating the tilt direction (propagation direction) of a displayregion.

In FIGS. 6A and 6B, a liquid crystal layer 3 is sealed between two glasssubstrates 1 and 2 having a predetermined cell gap and bonded oppositeto each other. Transparent electrodes (either of them is not shown) madeof ITO are respectively formed on the opposite surfaces of the twoopposite substrates 1 and 2. The plurality of alignment regulatingstructural members 4 of linear projections arranged at a pitch of 70 μmin parallel with each other are formed on the transparent electrode ofthe substrate 1. On the other hand, the plurality of alignmentregulating structural members 6 of linear projections arranged at thesame pitch as the alignment regulating structural members 4 and shiftedfrom the alignment regulating structural members 4 by a half pitch areformed on the transparent electrode of the substrate 2. The width ofeach of the alignment regulating structural members 4 and 6 is 10 μm andthe height thereof is 1.5 μm.

In space portions between the alignment regulating structural members 4,the alignment control factors 5 each having a height of 0.3 μm areextended at a pitch of 8 μm between the adjacent alignment regulatingstructural members 4. Liquid crystal monoacrylate monomer mixed liquidcrystal similar to the example 1-1 was inserted in the liquid crystallayer 3, and was cured by ultraviolet rays while a voltage of 5.0 V wasapplied. Vertical alignment film material X is used for the not-shownalignment films, and resist LC-200 of Shipley Co., Ltd. is used for theformation material of all the alignment regulating structural members 4and 6 and the alignment control factors 5. A cell gap is 4.0 μm.

Similarly to the example 1-1, although curing was carried out in thestate where singular points were generated on the main alignmentregulating structural members 4 and 6 of 1.5 μm, the alignmentdisturbance of the display region as shown in FIG. 75 was not produced.Incidentally, the tilt directions of the liquid crystal molecules in thespace portions between the alignment regulating structural members 4 and6 were the same as the example 1-1.

EXAMPLE 1-4

FIG. 7 shows a state in which a schematic construction of an MVA cellaccording to this example is viewed against a substrate surface. In FIG.7, a liquid crystal layer 3 (not shown) is sealed between two glasssubstrates 1 and 2 having a predetermined cell gap and bonded oppositeto each other. Transparent electrodes made of ITO are respectivelyformed on opposite surfaces of the two opposite substrates 1 and 2. Forexample, slit portions 8 and 9 formed by partially removing electrodematerial are provided on the transparent electrode 7 at the side of thesubstrate 1. The cruciform slit portion 8 having a width of 5 μm andconnecting the center points of respective opposite sides of arectangular cell functions as an alignment regulating structural member4. The plurality of slit portions 9 extending from the slit portion 8 inan oblique direction of 45° and having a width of 3 μm are formed at apitch of 8 μm, and these function as auxiliary alignment control factorsto suppress the disturbance of the orientation angle direction at thetime of tilting.

A cell was formed in which this substrate 1 and the substrate 2 havingITO formed on almost all the surfaces were bonded to each other, andliquid crystal monoacrylate monomer mixed liquid crystal similar to theexample 1-1 was sealed, and was cured by ultraviolet rays while avoltage of 5.0 V was applied. Vertical alignment film material X is usedfor the alignment film. The cell gap is 4.0 μm.

The liquid crystal molecules of the space portions at the time ofvoltage application are tilted in the directions parallel to theextending directions of the thin slit portions 9, and four domains areformed by the thick slit portion 8 as the boundary. At this time, onesingular point was merely formed at the center portion of the cruciformshape on the slit portion 8, and a singular point was not observed atother places. After curing by ultraviolet rays, the disturbance ofalignment as shown in FIG. 75 was not produced.

By using this example, very high-speed response characteristics in allgradations can be realized while an excellent alignment state is kept.

Second Embodiment

Next, a liquid crystal display according to a second embodiment of thepresent invention will be described with reference to FIGS. 8A to 18.This embodiment relates to a liquid crystal display in which liquidcrystal molecules are tilted in a direction of 0° or 45° with respect tothe extending direction of an alignment regulating structural membersuch as a projecting structural member or a slit portion of atransparent electrode, and alignment of the liquid crystal molecules isregulated by a liquid crystal skeleton by photo-curing or heat-curing ora non-liquid crystal skeleton.

As a vertical alignment type LCD, although an MVA-LCD using an alignmentregulating construction is put to practical use, there is a problem thatlight transmittance is lowered by the disturbance of the alignment ofliquid crystal molecules around the projecting structural member. Inorder to solve this defect, a singular point control type liquid crystaldisplay is proposed in a patent application (Japanese Patent ApplicationNo. 2000-60200) filed with Japanese Patent Office. A singular pointcontrol portion is formed to control the position of a singular point ofliquid crystal, so that the alignment disturbance of the liquid crystalmolecules is suppressed, and a drop in light transmittance issuppressed. As an example, a singular point control portion such as acruciform projection or an electrode slit portion is proposed. Besides,as another method for improving the light transmittance, a method isproposed in which a minute slit portion is formed on a transparentelectrode, and liquid crystal molecules are tilted parallel to the slitportion to prevent alignment disturbance, so that the drop in the lighttransmittance is prevented.

However, according to the above cruciform projection or the electrodeslit portion, or the minute projection or the minute electrode slitportion, there is a case in which there arises a problem that theresponse time becomes very slow though the luminance is improved ascompared with the general MVA-LCD. The reason why the response timebecomes slow will be described below.

FIGS. 8A to 13D show alignment states of liquid crystal molecules withrespect to alignment regulating structural members or singular pointcontrol portions. FIGS. 8A, 8C, 9A, 9C, 10A, 10C, 11A, 11C, 12A, 12C,13A and 13C show states of liquid crystal molecules 10 sealed betweentwo substrates 1 and 2 arranged opposite to each other, in section takenin a direction of a normal of a substrate surface. FIGS. 8B, 8D, 9B, 9D,10B, 10D, 11B, 11D, 12B, 12D, 13B and 13D show the states of the liquidcrystal molecules 10 viewed in the direction of the normal of thesubstrate surface. FIGS. 8A, 8B, 9A, 9B, 10A, 10B, 11A, 11B, 12A, 12B,13A and 13B show states of no voltage application in which a potentialdifference between transparent electrodes 11 and 12 formed on oppositesurfaces of the substrates 1 and 2 is zero, and FIGS. 8C, 8D, 9C, 9D, 10c, 10D, 11C, 11D, 12C, 12D, 13C and 13D show states of voltageapplication.

First, in FIGS. 8A to 8D, a slit portion 8 is formed on the transparentelectrode 12. When a voltage is applied between the electrodes 11 and12, the liquid crystal molecules 10 in the vicinity of the slit portion8 start to tilt, and the tilt of the liquid crystal molecules 10 isspread over the whole (see FIG. 8C). As shown in FIG. 8D, theorientation of the tilt is substantially orthogonal to the extendingdirection of the slit portion 8.

Similarly, in FIGS. 9A to 9D, an alignment regulating structural member4 of a linear projection is formed on the transparent electrode 12. Whena voltage is applied between the electrodes 11 and 12, the liquidcrystal molecules 10 in the vicinity of the structural member 4 start totilt, and the tilt of the liquid crystal molecules 10 spreads over thewhole (see FIG. 9C). As shown in FIG. 9D, the orientation of the tilt issubstantially orthogonal to the extending direction of the structuralmember 4.

In cruciform projections or slit portions for controlling the alignmentdisturbance or the minute electrode slit portions, since a distancebetween the adjacent projections or slit portions is short, tiltedliquid crystal molecules collide with each other, and the tilt directionof the liquid crystal molecule is changed. For example, in FIGS. 10A to10D, a slit portion 8 is formed on the transparent electrode 12. A slitportion 8′ orthogonal to the slit portion 8 is formed on the transparentelectrode 11. When a voltage is applied between the electrodes 11 and12, the liquid crystal molecules 10 in the vicinity of the slit portions8 and 8′ start to tilt, and the tilt of the liquid crystal molecules 10spreads over the whole (see FIG. 10C). As shown in FIG. 10D, theorientation of the tilt of the liquid crystal molecules 10 becomes adirection of 45° with respect to the extending directions of the slitportions 8 and 8′. Since a time is required for the change of the tiltdirection, the response time becomes extremely slow.

Similarly, in FIGS. 11A to 11D, a structural member 4 of a linearprojection is formed on the transparent electrode 12. A structuralmember 4′ of a linear projection orthogonal to the structural member 4is formed on the transparent electrode 11. When a voltage is appliedbetween the electrodes 11 and 12, the liquid crystal molecules 10 in thevicinity of the slit portions 8 and 8′ start to tilt, and the tilt ofthe liquid crystal molecules 10 spreads over the whole (see FIG. 11C).As shown in FIG. 11D, the orientation of the tilt of the liquid crystalmolecules 10 becomes a direction of 45° with respect to the extendingdirections of the structural members 4 and 4′. Since a time is requiredfor the change of this tilt direction, the response time becomesextremely slow.

In FIGS. 12A to 12D, minute slit portions 9 are formed on thetransparent electrode 12. When a voltage is applied between theelectrodes 11 and 12, the liquid crystal molecules 10 in the vicinity ofthe slit portion 9 start to tilt, and the tilt of the liquid crystalmolecules 10 spreads over the whole. As shown in FIGS. 12C and 12D, theorientation of the tilt becomes parallel to the extending direction ofthe slit portions 9. Since a time is required for the change of the tiltdirection, the response time becomes extremely slow.

Similarly, in FIGS. 13A to 13D, alignment control factors 5 of minutelinear projections are formed in the transparent electrode 12. When avoltage is applied between the electrodes 11 and 12, the liquid crystalmolecules 10 in the vicinity of the alignment control factors 5 start totilt, and the tilt of the liquid crystal molecules 10 spreads over thewhole (see FIG. 13C). As shown in FIG. 13D, the orientation of the tiltbecomes parallel to the extending direction of the alignment controlfactors 5. Since a time is required for the change of the tiltdirection, the response time becomes extremely slow.

Besides, there is a case where the minute slit portions 9 or thealignment control factors 5 directed toward two different directions areprovided in each pixel in order to realize a wide viewing angle. In thiscase, since a time is required for the liquid crystal molecules to bestably aligned at the boundaries of regions of the minute slit portions9 or the alignment control factors 5 having different directions, theresponse time becomes extremely slow.

Against the above problems, in this embodiment, a photo-curing orthermosetting component is mixed in a liquid crystal composition and isinjected into a liquid crystal panel, and light or heat is applied underapplication of a definite voltage, so that a three-dimensionalconstruction is formed of the cured material of the photo-curing orthermosetting component in the liquid crystal.

In the MVA-LCD, except for the vicinity of the projection or electrodeslit portion, the liquid crystal molecules are aligned vertically.Accordingly, at the instant when the applied voltage is changed, thefalling direction of the liquid crystal molecules is not determined, andthey can not fall down in any directions. On the other hand, when theprojection or the electrode slit portion is provided, at the voltageapplication, the liquid crystal molecules in the vicinity start to tiltin the direction perpendicular to the extending direction of theprojection or the electrode slit portion, and the tilt is successivelypropagated to the adjacent liquid crystal molecule to tilt the liquidcrystal molecules in the domain in the same direction.

FIGS. 14A and 14B show a state in which a liquid crystal panel includinga cruciform projection structural member 4 formed on one substrate 1 isviewed in the direction of a normal of a substrate surface. FIG. 14Ashows a state of the liquid crystal molecules 10 after voltageapplication immediately. Although liquid crystal molecules 10 in thevicinity of the structural member 4 start to tilt (hereinafter, called apropagation process) in the direction orthogonal to the extendingdirection of the structural member 4, since the tilt of the liquidcrystal molecules 10 is propagated from two directions different fromeach other by 90°, eventually, as shown in FIG. 14B, the liquid crystalmolecules are tilted (hereinafter, called a re-tilting process) in thedirection of 45° with respect to the extending direction of thestructural member 4. Since a time is required for the change of thistilt direction, the response time becomes extremely slow.

As described above with reference to FIGS. 8A to 14B, since all theliquid crystal molecules 10 do not respond to the application ofelectric field to the liquid crystal with the minimum movement towardthe final orientation, the response speed becomes slow. Then, the liquidcrystal molecules 10 are previously slanted in the direction of analignment after voltage application to such a degree that the contrastis not lowered. By this, the propagation process and the re-tiltingprocess are eliminated, and all the liquid crystal molecules 10 aremoved to the final alignment after the voltage application, so that theresponse time can be made short. Incidentally, in order to obtain asufficient contrast, it is desirable that this tilt angle is 85° orhigher when measured from the surfaces of the substrates 1 and 2.

As a method of previously tilting the liquid crystal molecules 10, aphoto-curing or thermosetting monomer is added to liquid crystal, and acured material is formed by polymerization of the monomer. Aphoto-curing or thermosetting liquid crystal of 0.1 wt % (weightpercent) to 3 wt % or a non-liquid crystal resin component is previouslymixed in the liquid crystal, and is injected into a liquid crystalpanel, and light or heat is applied to the liquid crystal panel while adefinite voltage is applied, so that the resin component is cured. Sincethe liquid crystal molecules 10 in the vicinity of the liquid crystalresin memorize the state where the voltage is applied, the response timecan be improved as described above.

In the case of the minute electrode slit portions 9, although thepropagation process hardly exists, at the boundaries of the slitportions 9 directed toward the different directions, the liquid crystalmolecules 10 immediately after the voltage application can be tilted intwo directions, so that the alignment of liquid crystal is disturbed.Although they are finally fixed in one direction, this re-arrangementprolongs the response time. If the liquid crystal molecules 10 arepreviously tilted in the direction of the final state of the liquidcrystal alignment by the photo-curing or thermosetting liquid crystalresin, the alignment disturbance of the liquid crystal molecules 10immediately after the voltage application is prevented and the responsecan be improved.

Hereinafter, specific examples will be described.

EXAMPLE 2-1

An XGA liquid crystal panel of a size of 15 inches in diagonal was madeon an experimental basis. FIG. 15 shows a state in which three pixels ofthe liquid crystal panel are viewed in the direction of a normal of asubstrate surface. For example, a not-shown TFT and a transparentelectrode (pixel electrode) 7 are formed at a side of a substrate 1, andlattice-like projection structural members 4 arranged at a predeterminedpitch are formed on the pixel electrode 7. A light shielding film 13, anot-shown color filter, and an opposite electrode are formed on the sideof an opposite substrate 2. Besides, lattice-like projection structuralmembers 6 having the same pitch as the lattice projection structuralmembers 4 and shifted by a half pitch from the lattice projectionstructural members 4 are formed on the opposite electrode.

Vertical alignment film material X is used for a not-shown alignmentfilm. The structural members 4 and 6 are formed of resist LC-200 ofShipley Co., Ltd. As liquid crystal, liquid crystal acrylate monomerUCL-001 of Dainippon Ink Co., Ltd. was added into liquid crystalmaterial A having a negative dielectric anisotropy, and after injection,ultraviolet rays were irradiated while a voltage was applied.

On the other hand, as a comparative example, a liquid crystal panel inwhich a photo-curing or thermosetting component was not added intoliquid crystal was made on an experimental basis. FIG. 16 is a graph inwhich the liquid crystal panel of this example and the liquid crystalpanel of the comparative example are compared with each other. Thehorizontal axis indicates the transmittance, and the vertical axisindicates the response time (ms). A solid line in the drawing indicatesthe liquid crystal panel of this example, and a broken line indicatesthe liquid crystal panel of the comparative example. As is apparent fromFIG. 16, according to this example, a short response time is obtained inthe range of all transmittance, and the response characteristics havebeen remarkably improved.

EXAMPLE 2-2

An XGA liquid crystal panel of a size of 15 inches in diagonal was madeon an experimental basis. FIG. 17 shows a state in which three pixels ofthe liquid crystal panel are viewed in the direction of a normal of asubstrate surface. For example, a not-shown TFT and a transparentelectrode (pixel electrode) 7 are formed at the side of a substrate 1,and minute slit portions 9 as shown in the drawing are formed on thepixel electrode 7. A light shielding film 13, a not-shown color filterand an opposite electrode are formed at the side of an oppositesubstrate 2.

Vertical alignment film material X was used for not-shown alignmentfilms. As liquid crystal, liquid crystal acrylate monomer UCL-001 ofDainippon Ink Co., Ltd. was added into liquid crystal material A havinga negative dielectric anisotropy, and after injection, ultraviolet rayswere irradiated while a voltage was applied.

On the other hand, as a comparative example, a liquid crystal panel inwhich a photo-curing or thermosetting component was not added intoliquid crystal was made on an experimental basis. FIG. 18 is a graph inwhich the liquid crystal panel of this example and the liquid crystalpanel of the comparative example are compared with each other. Thehorizontal axis indicates the transmittance, and the vertical axisindicates the response time (ms). A solid line in the drawing indicatesthe liquid crystal panel of this example, and a broken line indicatesthe liquid crystal panel of the comparative example. As is apparent fromFIG. 18, according to this example, a short response time is obtained inthe range of all transmittance, and the response characteristics havebeen remarkably improved.

Third Embodiment

A liquid crystal display according to a third embodiment of the presentinvention will be described with reference to FIGS. 19 to 22. In orderto improve the drop in the light transmittance caused by the alignmentdisturbance of liquid crystal molecules in the vicinity of theprojection structural members of the MVA-LCD already described in theprior art, and the low response speed caused by the slowness of theregulation of the tilt direction of liquid crystal molecules propagatedfrom the projection structural members at the time of voltageapplication, the method has been described in the first and secondembodiments in which the polymer structure is formed in the liquidcrystal and is solidified in the state of voltage application topreviously regulate the tilt direction of the liquid crystal, so thatthe alignment disturbance is prevented and speed-up is realized.

In order to prevent the alignment disturbance and to realize the highspeed response by the methods according to the first and secondembodiments, it is necessary to decrease the tilt angle (an averagepre-tilt angle; an average value of pre-tilt angles of liquid crystalmolecules arranged in the direction of a normal of a substrate;incidentally, the pre-tilt angle is an angle measured toward the normalof the substrate from the substrate surface) of liquid crystal moleculesafter solidification. However, if the average pre-tilt angle isdecreased, the black luminance is raised even at the time of no voltageapplication, and the high contrast, which is one of the greatestfeatures of the MVA-LCD, can not be realized.

Then, in this embodiment, at the time of formation of the polymerstructure by the cured material, masking is performed on the liquidcrystal panel, so that only the necessary portion is partially made alow pre-tilt region of a small pre-tilt angle and is solidified, and theremaining region is made to remain vertically aligned.

When only a portion where the alignment disturbance occurs, a portion onthe projection structural member, or a portion on a bus line electrodeis solidified in the state of voltage application, the alignmentdisturbance of the liquid crystal can be prevented, and the propagationof the tilt direction of the liquid crystal molecules can be madesmooth. Besides, since the ratio of the low pre-tilt region to the wholearea of the cell is small, and almost all the regions are formed in thelight shielding region, the drop in the contrast does not occur.

If the low pre-tilt regions are formed at constant intervals, thealignment regulating force by the region is propagated to the remaininghigh pre-tilt region as well, and the movement of the liquid crystalmolecules of the high pre-tilt region at the time of voltage applicationcan also be made smooth. By this, the prevention of the alignmentdisturbance of the liquid crystal and the speed-up of the response speedcan be realized while the high contrast is held.

Hereinafter, specific examples will be described.

FIG. 19 is a sectional view showing the liquid crystal panelconstruction according to this embodiment. Transparent electrodes 11 and12 are formed on opposite surfaces of opposite substrates 1 and 2 havinga predetermined cell gap and arranged opposite to each other. A liquidcrystal is sealed between the transparent electrodes 11 and 12. Aplurality of slit portions 8 (only one is shown in the drawing) areformed on the transparent electrode 12 at a predetermined pitch. Aplurality of alignment regulating structural members 4 of linearprojections are formed on the transparent electrode 11 at the same pitchas the slit portion 8 and are shifted from the slit portions 8 by a halfpitch.

The vicinities of the alignment regulating structural members 4 and theslit portions 8 become low pre-tilt regions 14 by the formation of thepolymer structure with cured material, and the remaining regions becomehigh pre-tilt regions 15 in which liquid crystal molecules 10 keep thesubstantially vertical alignment. As stated above, if the liquid crystalmolecules 10 are slightly tilted in the low pre-tilt regions 14 even atthe time of no voltage application, since the tilt direction of theliquid crystal molecules 10 immediately after the voltage application ispreviously determined, the propagation of the tilt is fast, and thealignment disturbance of the liquid crystal molecules does not occur.

Next, a manufacturing method of the low pre-tilt regions 14 and the highpre-tilt regions 15 in the liquid crystal panel construction shown inFIG. 19 will be described by use of FIGS. 20A to 20D. FIG. 20A shows apartial plane of a mask M used when ultraviolet light (UV light) isirradiated to a liquid crystal panel. An opening O is provided at apredetermined position of the mask M. FIG. 20B shows a state in which UVlight is irradiated to a liquid crystal panel P by using the mask M.

In the liquid crystal panel P, as a photo-curing resin, liquid crystalacrylate monomer UCL-001 of 1 wt % of Dainippon Ink Co., Ltd. is addedinto the host liquid crystal. A voltage of, for example, 6 V was appliedbetween electrodes at both sides of the liquid crystal of the liquidcrystal panel P, and UV irradiation was carried out through thepositioned mask M. UV light is irradiated to a predetermined position ofthe liquid crystal panel P through the opening O of the mask M. By this,the low pre-tilt region 14 is formed at the predetermined position.

Next, after the electrodes at both the sides of the liquid crystal areshort-circuited, as shown in FIG. 20C, UV irradiation is carried out tothe whole surface. By this, as shown in FIG. 20D, the high pre-tiltregions 15 are formed at positions other than the low pre-tilt region14.

FIG. 21 shows another example of the liquid crystal panel constructionaccording to this embodiment, and shows a state in which two adjacentliquid crystal cells are viewed against a substrate surface. Forexample, a not-shown TFT and a pixel electrode 7 are formed at a side ofa substrate 1. A light shielding film 13, a not-shown color filter andan opposite electrode are formed at a side of an opposite substrate 2. Aliquid crystal containing a photo-curing resin is sealed between thesubstrates 1 and 2.

In a not-shown photomask M used when a photo-curing material issolidified by UV light, an opening O is formed into a stripe shape. Byirradiating the liquid crystal cell with UV using this mask M, as shownin FIG. 21, low pre-tilt regions 14 each having a relatively thin widthand extending obliquely with respect to the end side of the pixelelectrode 7 are formed. High pre-tilt regions 15 are formed between thelow pre-tilt regions 14.

The liquid crystal molecule of the high pre-tilt region 15 has apre-tilt angle of 89°. The liquid crystal molecule of the low pre-tiltregion 14 has a pre-tilt angle of 85° by UV irradiation in a state inwhich a voltage of 5 V is applied to the liquid crystal. By adoptingthis construction, if a voltage is applied between the pixel electrode 7and the not-shown opposite electrode, since the liquid crystal moleculesof the high pre-tilt region 15 are smoothly moved in the directionpreviously regulated in the low pre-tilt region 14, a high speedoperation becomes possible, and the alignment disturbance of the liquidcrystal due to the irregularities of the structural members in thepixel, horizontal electric field and the like are reduced. Incidentally,it is desirable that the average pre-tilt angle in the high pre-tiltregion 15 is 88° or higher, and it is desirable that the averagepre-tilt angle in the low pre-tilt region 14 is from 45° to 88°.

In the conventional MVA-LCD, in the gradation change from black to adark halftone, the amount of change of applied voltage is low, and thechange of electric field in the liquid crystal is small, so that thepropagation speed of the tilt of the liquid crystal molecules becomeslow. According to this embodiment, it is expected that the effect ofimproving the drop of the propagation speed can also be obtained. Sincethe threshold voltage is lowered in the low pre-tilt regions 14, thepre-tilt regions 14 first respond at the time of low voltageapplication. Since the area rate of the low pre-tilt regions 14 is low,even if the low pre-tilt regions 14 become bright to some degree, thewhole luminance remains low. That is, although the whole has a lowluminance state, the low pre-tilt regions 14 make a high-speed response,and have a high luminance to some degree. As stated above, since theresponse of the low pre-tilt regions 14 becomes the response of thewhole cell, the high-speed response can be made even at a low gradation.Incidentally, it is desirable that the area of the high pre-tilt regions15 having the average pre-tilt angle of 88° or higher is 20% or more ofthe whole cell.

FIG. 22 shows still another example and a comparative example of theliquid crystal panel construction according to this embodiment, andshows a state in which two pixels of a liquid crystal panel are viewedin the direction of a normal of a substrate surface. For example, anot-shown TFT and a pixel electrode 7 are formed at a side of asubstrate 1, and lattice-like projection structural members 4 arrangedat a predetermined pitch are formed on the pixel electrode 7. A lightshielding film 13, a not-shown color filter and an opposite electrodeare formed at a side of an opposite substrate 2. Besides, lattice-likeprojection structural members 6 having the same pitch as thelattice-like projection structural members 4 and shifted by a half pitchfrom the lattice-like projection structural members 4 are formed on theopposite electrode.

For comparison, a cell of this embodiment was fabricated at the leftside in the drawing, and a cell of a conventional construction wasfabricated at the right side. First, in the cell of the conventionalconstruction at the right side, liquid crystal molecules are verticallyaligned at the time of no voltage application. In the state of voltageapplication, the liquid crystal molecules are urged to be alignedvertically to the projection walls of the lattice projection structuralmembers 4, and are soon changed in the direction of 45° with respect tothe lattice. Thus, the construction having the lattice-like projectionstructural members 4 and 6 has a very slow response speed, and thealignment disturbance of the liquid crystal is apt to occur.

On the other hand, the cell at the left side improves the problem, andlow pre-tilt regions 14 are formed around the lattice-like projectionstructural members 4 and 6. That is, the low pre-tilt region 14 isformed at the surrounding portion of each of regions surrounded by thelattice-like projection structural members 4 and 6, and surrounds a highpre-tilt region 15. Then, liquid crystal molecules 10 of the lowpre-tilt region are aligned and tilted at an orientation of 45° withrespect to the extending direction of the lattice. By this, at the timeof voltage application, since the liquid crystal molecules 10 of thewhole surface are smoothly tilted in the direction of 45°, a high-speedresponse becomes possible, and the alignment disturbance of the liquidcrystal molecules is prevented. Besides, since the liquid crystalmolecules 10 tilted at the time of no voltage application are only thosein the vicinity of the lattice-like projection structural members 4 and6, the drop in the contrast is also greatly reduced.

Not only the low pre-tilt regions 14 are formed to be divided like astripe shape or a lattice shape as described above, but also they may beformed so that a high pre-tilt region (for example, an average pre-tiltangle is 88° or higher) is dotted with low pre-tilt regions.

Besides, the low pre-tilt regions 14 may be naturally formed to berestricted to the structural members 4 and 6, such as the linearprojections or projection lattices, and their vicinities, or to the slitportions 8 and 9 and their vicinities.

Besides, although not shown, the low pre-tilt regions 14 may benaturally formed on a gate bus line, a data bus line, or an auxiliarycapacitance bus line formed on the liquid crystal panel.

Besides, the photomask M is divided into a plurality of regions having aplurality of transmission coefficients, and by performing mask exposurefor a predetermined time in a state where a predetermined voltage isapplied to the whole surface of the liquid crystal panel P, a pluralityof regions having a plurality of average pre-tilt angles may benaturally obtained at the same time.

Besides, it is desirable that the concentration of the photo-curingmonomer contained in the liquid crystal composition is 0.3 wt % to 3 wt%.

Fourth Embodiment

Next, a liquid crystal display according to a fourth embodiment of thepresent invention will be described with reference to FIGS. 23 to 34. Inthe MVA-LCD, by the existence of the alignment regulating structuralmembers for realizing alignment division, when a voltage is applied tothe liquid crystal cell, a plurality of unidirectional alignment regions(domains) are formed. Since the liquid crystal orientation is differentin every domain, a continuous transition in the liquid crystal directionoccurs at the boundary portion (domain wall). In the case where there isa transition (in-plane transition) in which the liquid crystalorientation is rotated in the substrate in-plane direction, in a minuteregion coincident with a polarization axis of one of polarizing platesarranged at upper and lower substrates in the relation of crossedNicols, since incident light is not subjected to birefringence, itbecomes a dark display. Besides, in the in-plane transition, since theliquid crystal orientation in the domain and the liquid crystalorientation of the domain wall are different from each other, adeviation (hereinafter called a φ deviation in this embodiment) from anideal orientation occurs in the liquid crystal orientation in thedomain, and the loss of transmittance occurs.

FIG. 23 shows a schematic sectional construction of a conventionalMVA-LCD. FIG. 23 shows a state in which electrodes 11 and 12 are formedon opposite surfaces of opposite substrates 1 and 2, and a liquidcrystal layer made of a large number of liquid crystal molecules 10 isformed between the electrodes 11 and 12. Two polarizing plates (notshown) are arranged in crossed Nicols at the outside of each of thesubstrates 1 and 2. As an alignment regulating structural member, alinear projection 4 having, for example, a width d=10 μm and a heightdh=1.2 μm is formed on the substrate 12.

According to this construction, although two domains in which the liquidcrystal orientations are different from each other by 180° are formed atboth sides of the linear projection 4, as shown in the drawing, thein-plane transition occurs at the domain wall, and there are liquidcrystal molecules 10 a and 10 b each having an orientation angle (angleof a major axis of a liquid crystal molecule when viewed against asubstrate surface) of 45°. The extending direction of the linearprojection 4 (in the drawing, the vertical direction to the paper plane)is made a standard, and in the case where polarizing plates are arrangedat the orientation of 45° in crossed Nicols, since birefringence doesnot occur in the vicinities of the liquid crystal molecules 10 a and 10b, a dark display is produced, and two dark lines are generally producedat both sides of the linear projection 4 in the extending direction.Besides, the orientation angle of a liquid crystal molecule 10 d in thedomain is different from the orientation angle of a liquid crystalmolecule 10 c of the domain wall by 90°, the φ deviation occurs in thewhole domain and the transmission loss occurs. As stated above, in theconventional structural member, the two dark lines and the drop in thetransmittance due to the existence of the φ deviation are great factorsto prevent the realization of high luminance.

With respect to the response speed, the MVA-LCD has excellentcharacteristics. However, there is only one problem that the response ofa halftone is slow. Since the region for regulating the alignmentdirection is only on the alignment regulating structural member, thepropagation of the liquid crystal tilt occurs over the whole domain. Thepropagation speed depends on the magnitude of the gradient of anelectric field generated on the alignment regulating structural member.Thus, at a halftone, since the electric field gradient on the alignmentregulating object is gentle, the propagation speed is low, andeventually, the response speed becomes slow.

Besides, the φ deviation in the domain has an influence on the responsespeed as well. By the liquid crystal molecules (for example, the liquidcrystal molecules 10 c to 10 a or 10 c to 10 b of FIG. 23) tilted in theextending direction of the alignment regulating structural member of thedomain wall, the deviation occurs in the orientation angle of the liquidcrystal molecules 10 of the domain. In the response process, at thepoint when all the liquid crystal molecules 10 are tilted, since adomain having an arbitrary deviation is produced and is mixed, thereoccurs a process in which a stable domain group is formed. As a result,in addition to a time in which all the liquid crystal molecules 10 aretilted, it becomes necessary to take a time in which the inside of thedomain is fixed, so that the response becomes slow. Especially, theresponse from full black to full white accompanying an abrupt changetends to generate a temporary φ deviation.

FIG. 24 shows another example of the sectional construction of theconventional MVA-LCD. The construction is the same as the constructionshown in FIG. 23 except that instead of the linear projection 4 formedon the electrode 12 shown in FIG. 23, a slit portion 8 formed byremoving a electrode material of an electrode 12 is provided as analignment regulating structural member. The slit portion 8 functionssimilarly to the linear structural member 4, and the MVA-LCD shown inFIG. 24 also has a problem that two dark lines and a φ deviation areproduced similarly to the foregoing.

In this embodiment, by using an alignment regulating structural memberwhich is effective in narrowing of the dark lines and in lowering oravoidance of the φ deviation, and makes an electric field gradient by analignment regulating structural member steeper, the high luminance andhigh speed response of an MVA-LCD are realized.

Hereinafter, specific examples will be described.

EXAMPLE 4-1

FIGS. 25 to 30 show examples of this embodiment.

An MVA-LCD shown in FIG. 25 is the same as the construction shown inFIG. 23 except that an alignment regulating structural member is made alinear projection 16 instead of the linear projection 4. The linearprojection 16 has a plurality of minute irregular portions in thevicinity of the apex in the extending direction. The sectional shape ofthe linear projection 16 is a two-peak shape in which the upper centerof a bank shape having a width d=10 μm and a height dh=2 μm is recessed.The distance d1 between two peaks is d1=3 μm, and the height d2 from thelower portion to the valley portion of the two peaks is d2=1 μm.

An MVA-LCD shown in FIG. 26 has the same construction as that shown inFIG. 24 except that an alignment regulating structural member is made aslit portion 17 instead of the slit portion 8. The slit portion 17includes a fine stripe-like electrode 18 along the extending direction.The stripe-like electrode 18 is formed to have a width d3=2.5 μm at thecenter of the slit portion having a width d=10 μm.

The linear projections 16 were formed at a pitch of 70 μm on theelectrode 12 of the substrate 2, and a not-shown alignment film wasformed to a thickness of 0.05 μm on the whole surface. On the otherhand, the slit portions 17 having the strip electrodes 18 were formed ata pitch of 70 μm on the electrode 11 of the substrate 1, and a not-shownalignment film was formed to a thickness of 0.05 μm on the wholesurface.

Next, after the upper and lower substrates 1 and 2 were bonded so thatthe linear projections 16 and the slit portions 17 were arranged to bealternately shifted from each other by a half pitch, liquid crystal wasinjected, so that an MVA cell having a cell gap of 4.0 μm was prepared.The positive resist (S1808; made by Shipley Far East Co., Ltd.),vertical alignment film material X, and liquid crystal material A havinga negative dielectric anisotropy were used for the linear projection 16,the alignment film, and the liquid crystal molecule 10, respectively.

As a comparative example, an MVA cell was prepared in which the linearprojections 4 shown in FIG. 23 were formed at a predetermined pitch atthe side of the substrate 1, and the slit portions 8 shown in FIG. 24were formed at the side of the substrate 2 to be shifted from the linearprojections 4 by a half pitch. The conventional MVA cell is fabricatedunder the same conditions as the MVA cell of this example except for thesectional shapes of the linear projection and the slit portion.

FIGS. 27 and 28 schematically show a section of the MVA cell accordingto this example. In the drawings, the illustration of the upper andlower substrates are omitted. The linear projection 16 is arranged onthe electrode 12 at the left side of FIG. 27, and the slit portion 17 isarranged at the right side. FIG. 28 shows a voltage distribution withequi-potential lines obtained when a predetermined voltage is appliedbetween both the electrodes 11 and 12 in the construction of FIG. 27. Asis apparent from the drawing, the equi-potential line over the upperportion of the linear projection 16 is changed so that it has themaximum value at the center and the minimum values at the right and leftthereof. Similarly, the equi-potential line below the lower portion ofthe slit portion 17 is changed so that it has the minimum value at thecenter and the maximum values at both sides thereof. That is, in theextending direction, at the top portion of the linear projection 16 inwhich the plurality of minute irregular portions in the verticaldirection are provided in the vicinity of the apex, and at the topportion of the slit portion 17, the minute domains are locally formedadjacently to both domains at both sides of the domain wall.

On the other hand, FIGS. 29 and 30 schematically show a section of theMVA cell according to the comparative example. The constructions of thedrawings are respectively the same as those of FIGS. 27 and 28. Thelinear projection 4 is arranged on the electrode 12 at the left side ofFIG. 29, and the slit portion 8 is arranged at the right side. FIG. 30shows a voltage distribution with equi-potential lines obtained when apredetermined voltage is applied between both the electrodes 11 and 12in the construction of FIG. 29. As is apparent from the drawing, theequi-potential line has only one extreme value at the upper portion ofthe linear projection 4 or the lower portion of the slit portion 8. Asstated above, since the equi-potential line at the upper portion of thelinear projection 4 or the lower portion of the slit 8 has only oneextreme value, there occurs an in-plane transition of 180° as shown inFIGS. 23 and 24.

On the other hand, according to this embodiment, by the irregularportion of the top of the linear projection 16 or the stripe electrode18 of the slit portion 17, the plurality of minute domains are locallyformed on the linear projection 16 or the slit portion 17. The minutedomains function to tilt the liquid crystal molecules on the linearprojection 16 or the slit portion 17 in the extending direction.Accordingly, according to the construction of this embodiment, theliquid crystal molecules on the linear projection 16 or the slit portion17 are tilted in the extending direction by alignment regulating forcehigher than the prior art. By this, the conventional in-plane transitionof 180° is divided into two liquid crystal orientation angle transitionsof 90°, and an angle difference in the liquid crystal orientation anglebetween the adjacent domains becomes small. As a result, the transitionlength of the domain wall becomes short, and narrowing of the dark linesis realized.

Incidentally, as the number of the irregularities of the upper portionof the linear projection 16 as the alignment regulating structuralmember or the number of the stripe electrodes 18 of the slit portion 17becomes large, the alignment regulating force of the minute domainsformed between the domains becomes high, and the distortion received bythe minute region from the adjacent domain becomes low. As a result, thetransition length of the domain wall becomes short as the number of theirregularities of the upper portion of the linear projection 16 or thenumber of the stripe electrodes 18 of the slit portion 17 becomes large,and narrowing of the dark lines is realized.

Besides, since the stability of the minute domains in which the liquidcrystal molecules are tilted in the extending direction of the linearprojection 16 or the slit portion 17, becomes high, the temporary φdeviation becomes slight, and more superior response characteristics canbe obtained.

According to the MVA cell of this example, it has been confirmed thatthe transmittance is improved by 10% or more as compared with theconventional MVA cell of the comparative example, and the dark linewidth is narrowed by 20% or more as compared with the comparativeexample. Besides, also with respect to the response characteristics, ithas been confirmed that the response of the halftone, which is theproblem, is faster than the comparative example by 10% or more.

In summary, the construction according to this example includes the pairof substrates 1 and 2 having a predetermined cell gap and arrangedopposite to each other, the electrodes 11 and 12 formed on the oppositesurfaces of the pair of substrates 1 and 2, as the alignment regulatingstructural member, at least one of the linear projection 16 providedwith the irregular portion formed in the vicinity of the top in theextending direction and arranged on the electrode 11 or 12 and the slitportion 17 formed by removing part of the electrode material of theelectrode 11 or 12 and provided with the stripe-like electrode 18 in theextending direction, the vertical alignment films formed between thepair of substrates 1 and 2, and the liquid crystal layer sealed betweenthe vertical alignment films and having the negative dielectricanisotropy.

EXAMPLE 4-2

FIGS. 31 to 33 show an example of this embodiment.

According an MVA-LCD shown in FIG. 31, in the MVA-LCD shown in FIG. 24,a conductive linear projection 19 is formed on the opposite substratejust above the conventional slit portion 8, and an alignment regulatingstructural member is constructed by the combination of the slit portion8 and the conductive linear projection 19. The other construction is thesame as the MVA-LCD shown in FIG. 24. The sectional shape of theconductive linear projection 19 has a bank shape with one peak having awidth d=5 μm and a height dh=2 μm. Both are disposed so that the edgeline of the conductive linear projection 19 is positioned at the centerof the slit portion 8.

The conductive linear projection 19 is fabricated by forming a linearprojection of an insulator having a predetermined width and a heightbefore the electrodes 11 and 12 on the substrates 1 and 2 are formed, bynext forming an electrode material on the whole surface, and bypatterning it. The conductive linear projections 19 are provided at apitch of 70 μm on the substrates 1 and 2. Besides, removed regions wereformed in the electrodes 11 and 12 at nearly center positions betweenthe adjacent conductive linear projections 19, and the slit portions 8were arranged. Next, a not-shown alignment film was formed to athickness of 0.05 μm on the whole surface.

Next, after both the substrates 1 and 2 were bonded to each other sothat the conductive linear projection 19 of one of the substrates wasopposite to the slit portion 8 of the other substrate, the liquidcrystal was injected, and the MVA cell of a cell gap 4.0 μm wasprepared. The alignment film and the liquid crystal material are thesame as those of the example 4-1. The conductive linear projection 19was fabricated by forming a transparent conductive film on an insulatingstructural member formed of a positive resist.

FIGS. 32 and 33 schematically show a section of the MVA cell accordingto this example. In the drawings, the illustration of the upper andlower substrates 1 and 2 is omitted. The slit portion 8 is arranged onthe electrode 12 at the left side of FIG. 32, and the conductive linearprojection 19 is formed at the position opposite to that. Since theconstruction shown at the right side of FIG. 32 is described in a nextexample, it is not described here. The left side of FIG. 33 shows avoltage distribution with equi-potential lines obtained when apredetermined voltage is applied between both the electrodes 11 and 12in the construction of FIG. 32. As is apparent from the drawing, in aregion linearly connecting the conductive linear projection 19 and theslit portion 8, an electric field generated between the upper and lowersubstrates becomes weak. Accordingly, even if the voltage is appliedbetween the electrodes 11 and 12, since a sufficient electric field totilt the liquid crystal molecules is not applied to the liquid crystalmolecules existing between the conductive linear projection 19 and theslit portion 8, they are not tilted in the extending direction of theconductive linear projection 19 and the slit portion 8, but remainsvertically aligned. By this, the liquid crystal molecules in thevicinity of the domain wall in this example are tilted through thevertical transition in which a polar angle is successively changed in aplane substantially orthogonal to the extending direction of theconductive linear projection 19 and the slit portion 8. That is, theliquid crystal transition of the domain wall becomes such a change thatin a state of a constant orientation angle, the polar angle approachesperpendicularity from 0°, and the orientation angle is inverted by 180°through the vertically aligned liquid crystal molecule of the centerportion.

As compared with the conventional slit portion construction, the tilt ofthe electric field generated on the structural member becomes steep, andthe liquid crystal molecules on the structural member becomes stable inenergy by the vertical transition rather than the in-plane transition.In the vertical transition, in the case where polarizing plates areformed in crossed Nicols in the orientation of 45° with respect to theextending direction of the alignment regulating object, the number ofdark lines on the structural member is changed from two to one. This isbecause there is no region where the orientation of incident light iscoincident with the orientation of liquid crystal, and only a region inwhich the liquid crystal at the center portion becomes vertical andbirefringence does not occur, becomes a dark line. Besides, there is noliquid crystal molecule falling down in the extending direction of thelinear projection, the liquid crystal orientation of the whole domainbecomes the ideal orientation, and the φ deviation does not occur. As aresult, the number of dark lines on the domain wall becomes one fromtwo, so that the transmission loss is reduced, the φ deviation isavoided, and the high luminance is realized. Besides, since the gradientof the electric field on the alignment regulating structural memberbecomes steep by the electrode slit portion and the conductivestructural member, the propagation speed of the tilt of the liquidcrystal of the domain becomes high, and more excellent responsecharacteristics can be obtained.

According to the MVA cell of this example, it has been confirmed thatthe transmittance is improved by 20% or more as compared with theconventional MVA cell of the comparative example, and the dark linewidth is narrowed by 20% or more as compared with the comparativeexample. It has been confirmed that the φ deviation in the domain isalso eliminated, and as compared with the transmittance of only thedomain of the comparative example, the transmittance is improved by 10%or more, and it is an almost ideal value. Besides, also with respect tothe response characteristics, it has been confirmed that the response ata halftone, which is the problem, becomes faster than the comparativeexample by 10% or more.

EXAMPLE 4-3

FIGS. 32 to 34 show an example of this embodiment.

The MVA-LCD shown in FIG. 34 is the same as the MVA-LCD shown in FIG. 31except that the slit portion 17 shown in FIG. 26 is provided instead ofthe slit portion 8 in the MVA-LCD shown in FIG. 31. However, the width dof the slit portion 17 is longer than that shown in FIG. 26, and d=22.5μm in this example, and the width d3 of the stripe-like electrode of thecenter portion of the slit portion 17 is d3=2.5 μm.

The right side of FIG. 32 and the right side of FIG. 33 schematicallyshow a section of the MVA cell according to this example. The slitportion 17 is arranged on the electrode 11, and the conductive linearprojection 19 is formed at the position opposite to that. The right sideof FIG. 33 shows a voltage distribution with equi-potential linesobtained when a predetermined voltage is applied between both theelectrodes 11 and 12 in the construction of the right side of FIG. 32.As is apparent from the drawing, since the electric field of the centerportion of the domain wall, that is, the electric field of the portionover the alignment regulating structural member is higher than that ofdomains at both sides, the liquid crystal molecules 10 between the slitportion 17 and the conductive linear projection 19 are tilted moregreatly than the liquid crystal molecules in the domain. By the highoblique electric field generated by the edge of the slit portion 17 andthe conductive linear projection 19, the tilt direction becomessubstantially parallel to the substrate surface in the plane orthogonalto the extending direction of the slit portion 17 and the conductivelinear projection 19 as shown in FIG. 34. The liquid crystal transitionin the domain wall becomes a change (horizontal transition) in which ina state of a constant orientation angle, the polar angle is graduallytilted, and through the maximum polar angle at the center portion, theorientation angle is inverted by 180°. As compared with the conventionalslit portion 8, the tilt of the electric field generated over theconductive linear projection 19 becomes steep, and the liquid crystalmolecules 10 over the conductive linear projection 19 become stable inenergy by the horizontal transition rather than the in-plane transition.In the horizontal transition, in the case where polarizing plates arearranged in crossed Nicols in the orientation of 45° with respect to theextending direction of the alignment regulating structural member, thenumber of dark lines over the alignment regulating structural memberbecomes 0 from two. This is because there is no region where theorientation of incident light is coincident with the orientation of theliquid crystal, and the liquid crystal molecules 10 vertically alignedat the center portion do not exist, and accordingly, there is no regionwhich is not subjected to birefringence. Besides, since the liquidcrystal molecules 10 which fall down in the extending direction of thealignment regulating structural member do not exist, the liquid crystalorientation of the whole domain becomes ideal, and the φ deviation doesnot occur. As a result, the number of dark lines on the domain wallbecomes zero from two, the transmission loss is reduced, the φ deviationis avoided, and the high luminance is realized.

Besides, the alignment regulating structural member by the combinationof the slit portion 17 and the conductive linear projection 19 has afunction of improving the response characteristics. Since the liquidcrystal molecules 10 of the domain wall center portion receive anelectric field higher than that in the domain, they are tilted moregreatly than the liquid crystal molecules 10 of the domain. That is, aseries of liquid crystal alignment transitions at the domain wall have,as shown in FIG. 34, an alignment distortion like a spray. Accordingly,even at a halftone, since the gradient of the electric field to theliquid crystal molecules becomes steep by the domain wall for regulatingthe propagation speed of the tilt of the liquid crystal, more excellentresponse characteristics can be obtained. Besides, by setting theapplied voltage at the time of black display to be a voltage lower thana predetermined threshold value, not 0 V, and by previously tilting theliquid crystal molecules 10 at the domain wall portion, the liquidcrystal molecules at the domain wall portion receive the electric fieldin an oblique direction, so that the response characteristics can beimproved more remarkably.

Since the dark line does not exist in the MVA cell of this example, thetransmittance is improved by 30% or more as compared with theconventional MVA cell of the comparative example. The φ deviation in thedomain is also eliminated, and as compared with the transmittance of thedomain of the comparative example, it has been confirmed that thetransmittance is improved by 10% or more and becomes an almost idealvalue. Also with respect to the response characteristics, it has beenconfirmed that the response of a halftone, which is the problem, is notlarger than half of the comparative example.

The functions, operations and effects according to the above examplesare shown in Table 1 while they are compared with the conventionalexample.

TABLE 1 Conventional Example Example 4-1 Example 4-2 Example 4-3 Liquidcrystal in-plane in-plane vertical horizontal transition transitiontransition transition transition Transmittance 1 1.1 1.2 1.3Transmittance 1 1   1.1 1.1 of only domain φ deviation present presentnot present not present of domain Width of 1 0.8 0.8 0   dark lineResponse speed 1 0.9 0.9 0.5

As described above, according to this embodiment, by using the alignmentregulating structural member effective in the narrowing of the darkline, and the reduction or avoidance of the φ deviation, the highluminance of the MVA-LCD can be realized, and the responsecharacteristics can be improved.

Fifth Embodiment

Next, a liquid crystal display according to a fifth embodiment of thepresent invention will be described with reference to FIGS. 35 to 37.This embodiment is an improvement of the liquid crystal display of theexample 4-3 of the fourth embodiment described with reference to FIG.34.

There is a case where the liquid crystal display of the example 4-3having the construction for realizing the horizontal transition can notobtain a sufficient effect in a low voltage region near the thresholdvoltage. Since the liquid crystal molecules 10 on the domain wall cannot be given the directionality tilted more greatly than the liquidcrystal molecules 10 in the domain at the threshold voltage or lower,they become unstable. Besides, even if the voltage is the thresholdvoltage or higher, in the case where the liquid crystal molecules 10 inthe domain are hardly tilted, they become unstable similarly. In theunstable state, there arises a problem that a possibility that the φdeviation occurs becomes high, and a sufficient improvement effectcannot be obtained in the response characteristics.

Besides, the construction shown in FIG. 34 has also a defect that amanufacturing margin is very narrow. When a position deviation of thealignment regulating structural members (the slit portion 17 and theconductive linear projection 19) respectively formed on the upper andlower substrates occurs by a bonding deviation at the time of bondingthe upper and lower substrates 1 and 2, the balance between adjacentdomains is lost, and a deviation from the ideal horizontal transitionoccurs. Especially, there arises a problem that the φ deviation becomesapt to occur, and the effect of high transmittance cannot besufficiently obtained. Besides, when the magnitude of the φ deviationbecomes different between adjacent domains by the bonding deviation,there arises a problem that a display blur occurs, or desired responsecharacteristics cannot be obtained.

In this embodiment, by using an alignment regulating structural memberin which a bonding deviation is hard to produce and a stable horizontaltransition can be realized even in a low voltage region, a highluminance and a high speed response are realized without narrowing amanufacturing margin.

Hereinafter, specific examples will be described.

EXAMPLE 5-1

FIGS. 35 and 36 show an example of this embodiment.

An MVA-LCD shown in FIG. 35 has the same shape as the MVA-LCD shown inFIG. 34 except that the conductive linear projection 19 in the MVA-LCDshown in FIG. 34 is replaced by a conductive linear projection 20.However, the width d of a slit portion 17 is longer than that shown inFIG. 26, and d=22.5 μm in this example, and the width d3 of astripe-like electrode at the center portion of the slit portion 17 isd3=2.5 μm.

The conductive linear projection 20 is such that a transparentconductive film is formed on a patterned novolac or acrylicphotosensitive resin. FIG. 36 shows a state in which the tip end portionof the conductive linear projection 20 is viewed in the directionorthogonal to the extending direction. As shown in FIG. 36, an irregularportion 21 in which irregularities are repeated in the extendingdirection is formed in the vicinity of the apex of the conductive linearprojection 20. The width (period) of the irregular portion 21 is d4=6.0μm, and the height (vertical difference) is d5=0.3 μm. The irregularportion 21 was formed by using heat shrinkage generated by irradiationof ultraviolet rays of irradiation energy of about 5000 mJ/cm² (λ=254nm) after the photosensitive resin was post-baked.

The irregular portion 21 provided at the top portion of the conductivelinear projection 20 can be regarded as a plurality of minute linearprojections extending in the direction orthogonal to the extendingdirection of the conductive linear projection 20. Thus, the liquidcrystal molecules 10 in the vicinity of the minute linear projectionsare aligned in the extending direction of the minute linear projections.

Accordingly, by using the alignment regulating structural member(combination of the slit portion 17 and the conductive linear projection20) of this example, also in the low voltage region, it becomes possibleto cause the liquid crystal molecules 10 on the domain wall to havedirectionality in the direction orthogonal to the extending direction bythe irregular portion 21 of the conductive linear projection 20. Bythis, it becomes possible to avoid or reduce the φ deviation which isapt to occur in the conventional construction, and the responsecharacteristics, together with the transmittance, are also improved.Besides, since a new alignment regulating force is exerted on the domainwall, the φ deviation produced by the bonding deviation can also bereduced. Accordingly, by applying this alignment dividing construction,a wide manufacturing margin can be secured, and the transmittance andthe response characteristics can be improved more remarkably.

As a comparative example, the MVA cell shown in FIG. 34 was prepared.The MVA cell has the same construction as the MVA cell of this exampleexcept that it has the conductive linear projection 19. Besides, in boththe present example and the comparative example, in order to confirm themargin to the bonding deviation, cells in which bonding was shifted werealso fabricated. As a result of alignment observations, according to theMVA cell of this example, the φ deviation, which occurred in the lowvoltage region, was capable of being made smaller than the comparativeexample, and more excellent transmittance characteristics and responsecharacteristics were obtained. Besides, it was confirmed that themagnitude of the φ deviation produced when the bonding deviationoccurred was also reduced.

EXAMPLE 5-2

FIG. 37 shows an example of this embodiment.

In an MVA-LCD shown in FIG. 37, the conductive linear projection 20 isnot formed on the substrate 1 in the MVA-LCD shown in FIG. 35, but slitportions 17 are formed at a pitch of 70 μm on the substrates 1 and 2.Then, a dielectric layer 22 of a positive resist having a thicknessd6=0.5 μm is formed on the electrode 12 in regions other than the slitportions 17 including stripe-like electrodes 18, and a verticalalignment film (not shown) having a thickness of 0.05 μm is formedthereon. The upper and lower substrates 1 and 2 are bonded to each otherso that the slit portions 17 are alternately arranged, and liquidcrystal is injected, so that the MVA cell of a cell gap of 4.0 μm isprepared.

By using the alignment regulating structural member of this example, thealignment division of the horizontal transition in which the problem dueto the bonding deviation does not arise can be realized. Since a step ofeliminating the deviation of the two opposite alignment regulatingstructural members and bonding the substrates can be simplified, a highmanufacturing yield can be obtained. As a result of alignmentobservations, in the MVA cell of this example, it was confirmed that theφ deviation did not occur in a region other than a low voltage region,and the φ deviation due to the bonding deviation, which occurred in thecomparative example, was prevented.

As described above, even if the bonding deviation of the substratesoccur, by using the alignment regulating structural member whichrealizes the horizontal transition more stable in energy, the highluminance and the high speed response can be realized without narrowingthe manufacturing margin of the MVA-LCD.

Sixth Embodiment

Next, a liquid crystal display according to a sixth embodiment of thepresent invention will be described with reference to FIGS. 38A to 43.The liquid crystal display according to this embodiment is an MVA-LCD inwhich an insulating linear projection is arranged as an alignmentregulating structural member, and has a feature that an electrode isformed on the linear projection. Besides, a potential such as decreasesa potential difference with respect to an electrode at the side of theopposite substrate is applied to the electrode on the linear projection.For example, the same potential as the potential of the oppositeelectrode is applied. By doing so, even if a voltage is applied betweenthe electrodes of both the substrates, the liquid crystal molecules onthe linear projection stand upright without being tilted in theextending direction of the linear projection. By this, the liquidcrystal molecules in the vicinity of the domain wall are tilted in thevertical transition in which the polar angle is successively changed inthe plane substantially orthogonal to the extending direction of thelinear projection. That is, the liquid crystal transition at the domainwall becomes a change in which in a state of a constant orientationangle, the polar angle approaches verticality from 0°, and through thevertically aligned liquid crystal molecule at the center portion, theorientation angle is inverted by 180°.

Hereinafter, specific examples will be described.

EXAMPLE 6-1

FIGS. 38A and 38B are sectional views showing a liquid crystal panelconstruction according to this example. FIG. 38A shows a panel sectiontaken along a normal of a panel surface, and FIG. 38B shows a stateviewed in the direction of the normal of the panel surface. Transparentelectrodes 11 and 12 are formed on opposite surfaces of a pair ofopposite substrates 1 and 2 having a predetermined cell gap and arrangedopposite to each other. A liquid crystal layer containing a large numberof liquid crystal molecules 10 is sealed between the transparentelectrodes 11 and 12. A plurality of linear projections 4 are formed ata predetermined pitch on the transparent electrode 12. A plurality oflinear projections 6 are formed on the transparent electrode 11 at thesame pitch as the linear projections 4 and are shifted by a half pitchfrom the linear projections 4. Two polarizing plates (either of them isnot shown) are arranged in crossed Nicols at the outside of each of thesubstrates 1 and 2. The cell gap is 4 μm, the height of the linearprojections 4 and 6 is 1.5 μm, the width is 10 μm, and the space (pitch)is 25 μm.

Electrodes 22 and 23 are formed on the top portions of the respectivelinear projections 4 and 6. The same potential as the potential appliedto the opposite electrode 11 is applied to the electrode 22 on thelinear projection 4. The same potential as the potential applied to theopposite electrode 12 is applied to the electrode 23 on the linearprojection 6.

For example, when 0 V is applied to the electrode 11 of the substrate 1and +5 V is applied to the electrode 12 of the substrate 2, the liquidcrystal molecules 10 are tilted in accordance with the distortion of theintensity of the electric field generated in the liquid crystal layer bythe action of the linear projections 4 and 6 as the alignment regulatingstructural members. However, since the potentials of the electrodes 22and 23 on the respective linear projections 4 and 6 are the same as thepotentials of the opposite electrodes, the same state as the state of novoltage application is kept on the respective linear protrusions 4 and6. Thus, the liquid crystal molecules 10 on the respective linearprojections 4 and 6 are not tilted but stand vertically. By this, theliquid crystal molecules 10 in the vicinity of the domain wall aretilted in the vertical transition in which the polar angle issuccessively changed in the plane substantially orthogonal to theextending direction of the linear projections 4 and 6. According to thisexample, panel characteristics were obtained in which the paneltransmittance was 5.2% and the response speed from black to gray of 25%was 77 (ms).

EXAMPLE 6-2

FIGS. 39A and 39B are sectional views showing a liquid crystal panelconstruction according to this example. A liquid crystal panel shown inFIGS. 39A and 39B is the same as the liquid crystal panel of the example6-1 except that the electrodes 23 on the linear projections 6 areremoved from the liquid crystal panel of the example 6-1 shown in FIGS.38A and 38B.

For example, when 0 V is applied to the electrode 11 of the substrate 1and +5 V is applied to the electrode 12 of the substrate 2, the liquidcrystal molecules 10 are tilted in accordance with the distortion of theintensity of the electric field generated in the liquid crystal layer bythe action of the linear projections 4 and 6 as the alignment regulatingstructural members. However, since the potentials of the electrodes 22on the respective linear projections 4 are the same as the potential ofthe opposite electrode, the same state as the state of no voltageapplication is kept on the respective linear projections 4. Thus, theliquid crystal molecules 10 on the respective linear projections 4 arenot tilted, but stand vertically. However, since the liquid crystalmolecules 10 on the respective linear projections 6 are tilted, theliquid crystal molecules 10 in the vicinity of the domain wall aretilted in a state which is close to the vertical transition though itsdegree is inferior to the example 6-1. According to this example, panelcharacteristics were obtained in which the panel transmittance was 5.0%and the response speed from black to gray of 25% was 105 (ms).

EXAMPLE 6-3

FIGS. 40A and 40B are sectional views showing a liquid crystal panelconstruction according to this example. A liquid crystal panel shown inFIGS. 40A and 40B is the same as the liquid crystal panel of the example6-1 except that slit portions 8 are provided instead of the linearprojections 4 of the liquid crystal panel of the example 6-1 shown inFIGS. 38A and 38B (slit width is 10 μm).

For example, when 0 V is applied to the electrode 11 of the substrate 1and +5 V is applied to the electrode 12 of the substrate 2, the liquidcrystal molecules 10 are tilted in accordance with the distortion of theintensity of the electric field generated in the liquid crystal layer bythe action of the linear projections 6 and the slit portions 8 as thealignment regulating structural members. However, since the potentialsof the electrodes 23 on the respective linear projections 6 are the sameas the potential of the opposite electrode, the same state as the stateof no voltage application is kept on the respective linear projections6. Thus, the liquid crystal molecules 10 on the respective linearprojections 6 are not tilted but stand vertically. However, since theliquid crystal molecules 10 on the slit portions 8 are tilted, theliquid crystal molecules 10 in the vicinity of the domain wall aretilted in a state which is close to the vertical transition though itsdegree is inferior to the example 6-1. According to this example, panelcharacteristics were obtained in which the panel transmittance was 5.0%and the response speed from black to gray of 25% was 110 (ms).

EXAMPLE 6-4

FIG. 41 is a sectional view showing a liquid crystal panel constructionaccording to this example. In a liquid crystal panel shown in FIG. 41,linear projections 6 are formed at a predetermined pitch on an electrode11, and linear projections 4 are formed on an electrode 12 at positionsopposite to the linear projections 6. Electrodes 22 are formed on everyother linear projections 4, and electrodes 23 are formed on every otherlinear projections 6 and are shifted from them by a half pitch. Theother construction is the same as the liquid crystal panel of theexample 6-1 shown in FIGS. 38A and 38B.

The same potential as the potential applied to the electrode 12 isapplied to the electrodes 22 on the linear projections 4. The samepotential as the potential applied to the electrode 11 is applied to theelectrodes 23 on the linear projections 6. That is, the construction issuch that the conductive linear projections provided with the electrodesare arranged at the opposite side of the linear projections 4 and 6 asthe alignment regulating structural members having no electrode on thetop portions.

For example, when 0 V is applied to the electrode 11 of the substrate 1and +5 V is applied to the electrode 12 of the substrate 2, 0 V isapplied to the electrodes 23 of the linear projections functioning asthe conductive linear projections, and +5 V is applied to the electrodes22 of the linear projections 4 functioning as the conductive linearprojections. By doing so, the alignment regulating force becomes high,and the response speed of display can be raised. According to thisexample, panel characteristics were obtained in which the paneltransmittance was 4.8% and the response speed from black to gray of 25%was 90 (ms).

EXAMPLE 6-5

FIG. 42 is a sectional view showing a liquid crystal panel constructionaccording to this example. In a liquid crystal panel shown in FIG. 42,linear projections 6 are formed at a predetermined pitch on an electrode11, and conductive linear projections 24 are formed at the same pitch asthe predetermined pitch and are shifted from the linear projections 6 bya half pitch. The conductive linear projections 24 are formed bystacking an electrode 11 on previously formed dielectric projections.

Besides, linear projections 4 are formed on an electrode 12 at the samepitch as the linear projections 6, and conductive linear projections 25are formed at the same pitch as the pitch and are shifted from thelinear projections 4 by a half pitch. The conductive linear projections25 are formed by stacking an electrode 12 on previously formeddielectric projections. The substrates 1 and 2 are bonded to each otherso that the linear projections 6 and the conductive linear projections25 are opposite to each other, and the linear projections 4 and theconductive linear projections 24 are opposite to each other. The otherconstruction is the same as the liquid crystal panel of the example 6-1shown in FIGS. 38A and 38B.

Since the operation of this example is the same as the example 6-4, thedescription is omitted. According to this example, panel characteristicswere obtained in which the panel transmittance was 4.8% and the responsespeed from black to gray of 25% was 90 (ms).

EXAMPLE 6-6

FIG. 43 is a sectional view showing a liquid crystal panel constructionaccording to this example. A liquid crystal display shown in FIG. 43 hasthe same construction as that of the example 6-5 shown in FIG. 42 exceptthat the shapes of the sections of the conductive linear projections 24and 25 in the direction orthogonal to the extending direction aredifferent.

The shape of the section of each of the conductive linear projections 24and 25 in the direction orthogonal to the extending direction ischaracterized in that an upper side is longer than a lower side, and thearea of an upper surface of each of the conductive linear projections 24and 25 is larger than the area of a surface being in contact with thepixel electrode on which the projection is arranged. By doing so, thealignment direction by the projections becomes more stable, and theresponse speed of display can be further raised. Incidentally, theconductive linear projections 24 and 25 can be formed by overexposureusing a negative photosensitive material.

Besides, the conductive linear projections 24 and 25 can be formed byforming color filter layers in piles at the time of formation of colorfilters, and by forming transparent electrodes thereon. Accordingly, theconductive linear projections 24 and 25 can be formed without increasingthe manufacturing step. According to this example, panel characteristicswere obtained in which the panel transmittance was 4.8% and the responsespeed from black to gray of 25% was 70 (ms).

CONVENTIONAL EXAMPLE

A conventional MVA-LCD was formed in which linear projections wereformed on the opposite substrate to be shifted by a half pitch. Thepanel construction parameters such as a cell gap are the same as thoseof the example 6-1. The panel transmittance was 4.8%. The response speedfrom black to gray of 25% was 120 (ms).

The functions, operations and effects of the above examples are shown inTable 2 while they are compared with the conventional example.

TABLE 2 Conventional Example Example Example Example Example Exampleexample 6-1 6-2 6-3 6-4 6-5 6-6 Panel 4.8 5.2 5.0 5.0 4.8 4.8 4.8transmittance (%) Halftone 120 77 105 110 90 90 70 response time (ms)

Seventh Embodiment

Next, a liquid crystal display according to a seventh embodiment of thepresent invention will be described with reference to FIGS. 44 to 54. Inorder to improve the transmittance characteristics of an MVA-LCD, asystem is proposed in which the orientation of liquid crystal alignmentof a structural member or a slit portion is made different from theorientation of liquid crystal alignment of a space (region between twostructural members) portion by 45°. This system can be realized byforming, for example, lattice-like alignment regulating structuralmembers 4 and 6 on upper and lower substrates as shown in FIG. 44,arranging the structural members 4 and 6 of the upper and lowersubstrates to be shifted from each other by a half pitch, and loweringthe height of each of the structural members 4 and 6 to approximatelyhalf of that of the conventional MVA-LCD. Two polarizing plates at bothsides of the upper and lower substrates are arranged in crossed Nicols,and are arranged so that both polarization axes become orthogonal to orparallel to the extending direction of the structural members 4 and 6.By doing so, a deviation between the orientation of the liquid crystalalignment in the domain and the orientation of the liquid crystalalignment on the alignment regulating structural member can be madesmaller than that of the conventional MVA-LCD. Thus, the deviation ofthe liquid crystal molecules from the ideal orientation in the domainbecomes small, the number of dark lines can be made one, and thetransmittance can be improved.

However, in this system, although the transmittance can be improved ascompared with the conventional type, there arises a problem that theresponse speed becomes slow. Then, a response state of a cell wasobserved by using a high speed camera. FIGS. 45A, 45B, 45C, 46A, 46B,46C, 46D, 47A, 47B, and 47C show results of response states of a cellafter a predetermined time has passed after voltage application. InFIGS. 45A to 47F, each of the drawings shows a plurality of domainsdivided by the alignment regulating structural members 4 and 6 shown inFIG. 44. FIGS. 45A to 45C in turn show states after 0 ms, 12 ms, and 16ms have passed since the start of the voltage application, FIGS. 46A to46D in turn show states after 20 ms, 40 ms, 100 ms and 200 ms havepassed, and FIGS. 47A to 47C in turn show states after 400 ms, 500 ms,and 700 ms have passed.

By the observation results, it has been understood that the followingthree factors are factors of slow response.

1. (See problem 2 of FIG. 46A) It is seen that a complicated opticalpattern appears at the center portion of the space at the initial periodof response, and it assimilates with the brightness of the surroundingsand gradually becomes bright with the passage of time. It has been foundthat the cause is such that liquid crystal molecules in the vicinity ofthe center of the space portion do not follow the alignment regulationfrom the structural member at the initial period of the response and arealigned at random, however, they receive the propagation of the tiltfrom the liquid crystal molecules in which the alignment is regulated bythe structural member with the passage of time, and are graduallyaligned in the regulation direction of the structural member.

2. (See problem 3 of FIG. 46A) In regions very close to the structuralmember or the slit, a region other than a crossing portion is darkimmediately after the response, and becomes bright with the passage oftime. It has been found that the cause is such that the liquid crystalmolecules of this region are aligned in the orthogonal (90°) orientationwith respect to the extending direction of the linear structural memberor slit portion immediately after the response, and thereafter, thealignment is changed to the orientation of 45°.

3. (See problem 1 of FIG. 46B) It is seen that immediately after theresponse, among regions on the structural member or the slit portion, aplurality of singular points of alignment vectors appear in the crossingportion and regions other than that, and with the passage of time, thesingular points appearing in the regions other than the crossing portionare moved so as to attract each other and disappear. Further, inaccordance with the movement and extinction of the singular points,there is a change in the brightness of the surroundings (three darklines are changed to one line). The reason of this will be describedbelow. At the time of voltage application, the liquid crystal moleculeson the linear structural member or the slit portion are urged to bealigned in the direction parallel to the extending direction of thestructural member or the slit portion. Here, for example, in the casewhere a line is extended right and left, there are two cases, that is, aleft direction and a right direction, in which the liquid crystalmolecules are aligned parallel to that. In the vicinity of the crossingportion of the structural member or the slit portion, since an alignmentcontrol state is realized in which a singular point of an alignmentvector is stably formed, the alignment orientation of the liquid crystalmolecules is determined to be one direction in accordance with that.However, at the regions other than the crossing portion, there is nomeans for determining the orientation of the liquid crystal alignment.Thus, it is conceivable that immediately after the response, the liquidcrystal molecules in the regions other than the crossing portion areslanted in one of the two directions at random, so that singular pointsare produced in the regions other than the crossing portion, andthereafter, the alignment state is changed in accordance with thealignment orientation of the crossing portion, and the singular pointsother than those on the crossing portion in which the singular point canbe stably formed, finally disappear.

In summary, the cause of making the response slow can be classified intothree factors, that is, the random alignment in the space portion, theorthogonal alignment in the vicinity of the structural member, and thechange (movement and disappearance) of the singular points produced inthe regions other than the crossing portion of the lattice.

Then, according to this embodiment, in order to improve the responsecharacteristics of the MVA-LCD for controlling the liquid crystalalignment by the linear projection or the slit portion provided on thesubstrate, the liquid crystal molecules on the linear projection or theslit portion are made not to be vertically aligned even at the time ofno voltage application. By this, at the time of no voltage application,the tilt direction of the liquid crystal molecules on the linearprojection or the slit portion can be determined in advance.

As a result, also after the voltage application, since the liquidcrystal molecules on the linear projection or the slit portion followthe previously determined tilt direction, the movement and disappearanceof the singular points, which occurred in the conventional MVA-LCD, canbe eliminated.

Further, at the time of the voltage application, the liquid crystalmolecules of the region adjacent to the linear projection or the slitportion are urged to be aligned in the orientation of 45° with respectto the extending direction of the linear projection or the slit portion.At this time, since the liquid crystal molecules on the linearprojection or the slit portion are tilted in the previously determinedorientation, the liquid crystal molecules in the region adjacent to thiscan change the alignment smoothly from the tilt orientation to thedirection shifted by 45°. By these, the above problems 2 and 3 can beimproved and the response speed can be raised.

Incidentally, in order to obtain a bright display having high contrast,it is appropriate that the alignment orientation of the liquid crystalmolecules on the linear projection or the slit portion is shifted by 45°with respect to the alignment orientation of the liquid crystalmolecules in the domain at the time of voltage application. Besides, itis necessary that the polarization axis of a polarizing plate is alsoarranged to be in the orientation of 45° with respect to the alignmentorientation of the liquid crystal molecules in the domain. If theorientation of the liquid crystal alignment on the linear projection orthe slit portion is shifted by 45° from the alignment orientation of theliquid crystal molecules in the domain, the orientation of thepolarization axis is coincident with the orientation of the liquidcrystal alignment on the linear projection or the slit portion, and alight leak does not occur. If the alignment orientation of the liquidcrystal molecules on the linear projection or the slit portion areshifted from the orientation of the polarization axis, the light leakoccurs at the time of a black display. Thus, as a method of preventingthe light leak from occurring, at least one of the linear projection orthe slit portion, and their opposite portions may be shaded.

Besides, at the time of the voltage application, the linear projectionor the slit portion is made the boundary, and the alignment orientationsof adjacent liquid crystal domains are different from each other byapproximately 90°. The alignment orientation of the liquid crystalmolecules on the linear projection or the slit portion at the time of novoltage application is equal to the extending direction of the linearprojection or the slit portion. Besides, a difference between theorientation of the pre-tilt angle appearance of the liquid crystalmolecules on the linear projection or the slit portion at the time of novoltage application and the alignment orientation of the liquid crystaldomains positioned at both sides of the boundary of the linearprojection or the slit portion at the time of voltage application is 90°or less.

Hereinafter, specific examples will be described.

EXAMPLE 7-1

A liquid crystal panel construction according to this example will bedescribed with reference to FIGS. 48A and 48B. FIGS. 48A and 48B showstates in which a liquid crystal panel according to this example isviewed against a substrate surface, FIG. 48A shows the state at the timeof no voltage application, and FIG. 48B shows the state at the time ofvoltage application.

Lattice-like alignment regulating structural members 4 (6) were formedon a substrate having an ITO electrode. Photosensitive acryl resin wasused for a structural material. The formation of a structural patternwas performed by spin coating the resin on the substrate, carrying outbaking at 90° C. for 20 minutes (using clean oven), selectivelyirradiating ultraviolet light by using a photomask, carrying outdevelopment with an organic alkali developer (solution of TMAH of 0.2 wt%), and carrying out baking at 200° C. for 60 minutes (using cleanoven). The width of the structural member 4 (6) was made 5 μm, theheight was made 0.74 μm, and the lattice pitch was made 40 μm.

By coating the thus obtained substrate with an alignment film directlywithout carrying out an ashing processing, the alignment film was madenot to be selectively formed on the structural member 4(6). Verticalalignment film material X was spin coated on the substrate, and afterpre-baking was carried out at 110° C. for one minute (using hot plate),primary baking was carried out at 180° C. for 60 minutes (using cleanoven). The two substrates formed in this way were bonded to each otherso that the pitches of the lattices are shifted from each other by ahalf pitch to form a cell, and liquid crystal material A having anegative dielectric anisotropy was injected between the substrates. Thecell gap was made 4 μm. The alignment state of the cell was observed,and as shown in FIG. 48A, it was confirmed that the liquid crystalmolecules 10 positioned on the structural members 4 and 6 were notvertically aligned at the time of no voltage application. Incidentally,the thickness of the alignment film at the alignment regulatingstructural member or at the opposite portion may be made thinner thanthe thickness in the region where the alignment regulating structuralmember does not exist.

Next, as a comparative example, a panel was fabricated in which anashing processing of about one minute was carried out in an oxygenplasma atmosphere to the substrate before coating of the alignment film,so that the alignment film was formed on the structural member as well.

Next, response states of both were observed by a high-speed camera. Theobservation results will be described again with reference to FIGS. 45Ato 47F. FIGS. 45A, 45B, 45C, 46A, 46B, 46C, 46D, 47A, 47B and 47C showresults of the response states of the cell after a predetermined timehas passed after voltage application in the comparative example. FIGS.45D, 45E, 45F, 46E, 46F, 46G, 46H, 47D, 47E and 47F show results of theresponse states of the cell after a predetermined time has passed aftervoltage application in this example. Incidentally, for facilitating anunderstanding through the drawings, in the respective drawings of FIGS.45D, 45E, 45F, 46E, 46F, 46G, 46H, 47D, 47E and 47F, domains to benoticed are surrounded by circles.

First, at the time of no voltage application, in this example, althoughthe liquid crystal molecules on the structural member are not verticallyaligned, since the orientation is equal to the orientation of thepolarization axis, similarly to the comparative example in which theliquid crystal molecules on the structural member are verticallyaligned, a black display state appears (see FIGS. 45A and 45D).

Next, when the brightness in the vicinity of the structural member aftervoltage application is compared, the whole in the vicinity of thestructural member is already bright after 12 ms in the example, whereasonly the portion in the vicinity of the crossing portion is bright inthe comparative example (see FIGS. 45B and 45E).

Besides, when the state of singular point formation on the structuralmember after voltage application is compared, a singular point is notseen in a portion except the crossing portion of the structural membersin this example, whereas a singular point is also formed at a linearportion between the crossing portions, and it is understood that thesingular point disappears after a long time of 700 ms or more (see FIGS.47C and 47F).

Next, measurement results of response speed are shown in FIGS. 49A and49B. FIG. 49A is a graph in which the horizontal axis indicates therelative transmittance (%), and the vertical axis indicates the responsespeed (ms). Incidentally, the relative transmittance is made 100% whenan applied voltage to the liquid crystal is 5.4 V. FIG. 49B numericallyshows measurement values of response speed at respective measurementpoints of the relative transmittance (%). As is apparent from FIGS. 49Aand 49B, in this example, the response speed higher than those of thecomparative example is obtained at any gradations, and this fullycorresponds to the results by the high speed camera shown in FIGS. 45Ato 47F. By these, it is understood that the response characteristics canbe improved by this embodiment.

EXAMPLE 7-2

FIG. 50A shows a panel construction according to this example, and FIG.50B shows a panel construction according to a comparative example. Thisexample is the same as the panel construction of the example 7-1 shownin FIGS. 48A and 48B except for the following. In the comparativeexample shown in FIG. 50B, lattice-like alignment regulating structuralmembers 4 and 6 having an equal width are formed on upper and lowersubstrates. On the other hand, in this example, as shown in FIG. 50A,the widths of lattice-like alignment regulating structural members 34and 36 are changed in the extending direction. The width of a thickportion of the lattice-like alignment regulating structural members 34and 36 was made 5 μm, and the width of a thin portion was made 2 μm. Bythis, the liquid crystal alignment on the structural members 34 and 36can be controlled to be in a definite direction. Here, the thickness atthe crossing portion of the structural members on the same substrate wasmade thickest, and the liquid crystal alignment on the structuralmembers could be controlled to be within 90° from the liquid crystalalignment in the domain (45° in this example). As in the comparativeexample, in the case where the width of the structural member isconstant, since either direction with respect to the extending directioncan not be set for the tilt orientation of the liquid crystal moleculeson the structural member, there is a case where the tilt orientation ofthe liquid crystal molecule on the structural member becomes 90° or morewith respect to the alignment orientation of the space portion at thetime of voltage application (liquid crystal molecules colored black inthe drawing). In this case, an alignment abnormality as shown at thelower portion of the center (below the outside of a circular portion) ofFIGS. 45D, 45E, 45F, 46E, 46F, 46G, 46H, 47D, 47E and 47F is observed,and the transmittance is lowered. However, by changing the width of thestructural member as in this example, a desired direction can be stablyset for the liquid crystal alignment of the structural member, so thatthe drop in the transmittance can be suppressed.

EXAMPLE 7-3

FIG. 51A shows a state in which a panel construction according to thisexample is viewed against a substrate surface. FIG. 51B shows a sectiontaken along line A-A of FIG. 51A. This example is the same as the panelconstruction of the example 7-1 shown in FIGS. 48A and 48B except thatthe height of the lattice-like alignment regulating structural members 4and 6 is changed. In this example, the height of a crossing portion ofthe structural member on the same substrate was made highest, the heightof a high portion was made 1.2 μm, and the height of a low portion wasmade 0.5 μm. In FIG. 51B, the height of a crossing portion 37 of thelattice-like alignment regulating structural member 4 on the substrate 2is made highest. Similarly to the example 7-2, also by the constructionof this example, the liquid crystal alignment on the structural membercan be stably set to have a desired direction, and the drop in thetransmittance can be suppressed.

EXAMPLE 7-4

FIGS. 52A and 52B show a panel construction of this example. FIG. 52Ashows a state in which the panel construction according to this exampleis viewed against a substrate surface. FIG. 52B shows a section takenalong line A-A of FIG. 52A. This example is the same as the panelconstruction of the example 7-1 shown in FIGS. 48A and 48B except that aplurality of minute structural members 40 are formed on the lattice-likealignment regulating structural members 4 and 6, and an alignment film41 is formed thereon.

Each of the minute structural members 40 has, as shown in FIG. 52A, ashape of an isosceles triangle when viewed against a substrate surface.The minute structural members 40 are arranged so that the bottom side ofthe shape of the isosceles triangle is directed toward the side of thecrossing portion 37 of the structural members 4 and 6. By this, sincethe liquid crystal alignment on the structural member can be stably setto have a desired orientation, the drop in the transmittance can besuppressed.

EXAMPLE 7-5

This example will be described with reference to FIG. 53. In FIG. 53,ultraviolet ray irradiation was carried out, while the substrates 1 and2 were selectively shaded with a photomask M, so that only thestructural member 4 and its opposite portion were irradiated withultraviolet light. The wavelength of ultraviolet light was made 254 nm,and the irradiation amount was made about 5000 mj/cm². By this, apre-tilt angle of the liquid crystal molecule 10 on the structuralmember 4 could be made to be approximately 0° (the liquid crystalmolecule 10 is aligned substantially parallel to the substrate surface).In the case where the pre-tilt angle is 0°, the drop in thetransmittance due to the difference of the tilt angle does not occur.

EXAMPLE 7-6

This example will be described with reference to FIG. 54. This exampleis the same as the construction of the example 7-1 except for thefollowing. A rubbing processing was selectively carried out onto thestructural members 4 and 6. Rubbing directions 46 (indicated by arrowsin the drawing) were parallel to the extending directions of the linearstructural members 4 and 6, and the processing was carried out from theinside of the crossing portion 37 to the outside. By this, since theliquid crystal alignment on the structural members 4 and 6 can be stablyset to have a desired orientation, the drop in the transmittance can besuppressed.

As described above, according to this embodiment, the responsecharacteristics in the liquid crystal display for controlling the liquidcrystal alignment can be improved by the structural member or the slitportion provided on the substrate.

Eighth Embodiment

Next, a liquid crystal display according to an eighth embodiment of thepresent invention will be described with reference to FIGS. 55 to 62.This embodiment shows optimum structural conditions of a liquid crystalpanel capable of improving the display response speed of an MVA-LCD. Anexample of liquid crystal panel conditions of a conventional MVA-LCD issuch that a cell gap d is 4.0 μm, and Δn (refractive index anisotropy)of liquid crystal is 0.0822. In the conventional MVA-LCD, since acontrast ratio when viewed from the front is very high, a viewing anglecharacteristic is very wide, and a response property between white andblack is also fast, it is excellent as a still picture monitor of a PC(Personal Computer) or the like. However, since the response speed at ahalftone (gray scale) is not good, if it is used as a monitor for copingwith motion pictures, there is a case where “persistence of vision” and“display blur” occur.

FIGS. 55 and 56 are views for explaining a problem to be solved by thisembodiment. In FIG. 55, the horizontal axis indicates the attainedtransmittance (%), and the vertical axis indicates the response speedTon (ms; millisecond), and in the MVA-LCD, the drawing shows theresponse speed Ton from a zero gradation at which start transmittance isabout 0% and a display screen is fully black to the attainedtransmittance of a predetermined gradation.

In FIG. 56, the horizontal axis indicates the start transmittance (%)after the change of gradation, and the vertical axis indicates theresponse speed Toff (ms), and in the MVA-LCD, the drawing shows theresponse speed Toff from a predetermined gradation to a display screenof fully black in which the attained transmittance is about 0%.

As is apparent from FIG. 55, there is a halftone at which the responsespeed Ton at the time when the black display is changed to gray(halftone) exceeds 100 ms. Besides, as is apparent from FIG. 56, thereis a halftone at which the response speed Toff at the time when thehalftone is changed to black exceed 20 ms. Especially, at the lowresponse speed of Ton, when the liquid crystal monitor is made toproduce a motion picture display, line (tail) draw or the like occurs,and a satisfactory motion display can not be obtained.

The MVA system using the vertically aligned liquid crystal moleculesuses an ECB effect (Electric-field Control Birefringence effect), and ingeneral, the response speed τ relating to the electro-opticcharacteristics is given by the following expression.τ_(r)=η_(i) d ²/(∈₀ ·|Δ∈|V ² −K ₃₃π²)τ_(d)=η_(i) d ²/(K ₃₃π²)τ_(r): rising time (MVA: black→white)τ_(d): falling time (MVA: white→black)η_(i): viscosity parameterK₃₃: elastic parameter (bend)d: cell gap∈₀: relative dielectric constantΔ∈: dielectric anisotropy (liquid crystal material)V: applied voltage

The above expression means that if the viscosity of the liquid crystalmaterial is made low, the cell gap is made small, the dielectricanisotropy of the liquid crystal material is made large, the appliedvoltage is made high, or the elastic constant is made small, theresponse speed τ of the liquid crystal cell becomes small and theresponse performance of the MVA-LCD is improved.

Conventionally, attempts to raise the response speed by decreasing thecell gap d of the MVA-LCD and decreasing the viscosity of the liquidcrystal have been made. Especially, as is apparent from the aboveexpression, if the cell gap d is made small, the effect can be obtainedby the square thereof.

However, if the cell gap d is simply made small, the transmittance ofthe liquid crystal cell is lowered, and the display of the liquidcrystal monitor or the like becomes dark. In order to prevent this, incompensation for the small cell gap d, it is necessary to use liquidcrystal having large Δn. However, in the liquid crystal material havinglarge Δn and a negative dielectric anisotropy, its viscosity is apt tobecome relatively large, and it becomes necessary to prevent this to aminimum.

Besides, in the MVA-LCD, even if the cell gap d is simply made small orthe applied voltage is made high, as is pointed out in the foregoingembodiments, there is a case where the response time τ can not be madehigh by the alignment deviation (φ deviation) of liquid crystalmolecules generated in the vicinity of the linear projection (bank) orthe slit portion as the alignment regulating structural member. In orderto avoid this and to make the cell gap d small, it is necessary toprovide an alignment regulating structural member meeting variousconditions.

Incidentally, in general, when the cell gap d becomes small, a timerequired for injecting liquid crystal into a space between two oppositeglass substrates becomes long. Especially, the viscosity of the verticalalignment type liquid crystal used for the MVA system is apt to becomerelatively large and the time of liquid crystal injection becomes long.Accordingly, when the cell gap d is made small in the MVA-LCD, therearise a problem that a disadvantage occurs in mass production ascompared with the TN type LCD or the like. Thus, it is necessary toadopt an MVA-LCD manufacturing method in which even if the cell gap d ismade small, the disadvantage does not occur in the mass productionprocess, and the manufacturing cost is also made equivalent or can bereduced.

FIG. 57 is a graph showing the dependency of response characteristics ofa liquid crystal display on the cell gap (cell thickness). Thehorizontal axis indicates the attained transmittance (%), and thevertical axis indicates the response speed Ton (ms). Table 3 shows therelation between the attained transmittance and the response speed Tonat respective cell thicknesses of the graph of FIG. 57. Incidentally,the liquid crystal material of the MVA-LCD shown in FIG. 57 and Table 3,the back height and bank width of a bank-like alignment regulatingstructural member, and the gap width of the bank are formed under thesame conditions as the MVA-LCD having the characteristics of FIGS. 55and 56.

TABLE 3 Transmittance Cell Cell Cell (%) thickness = 2 μs thickness = 3μs thickness = 4 μs 2.5 52 103 180 5 36 72 132 10 30 68 121 15 24 61 11225 19 47 85 50 26 29 55 75 55 20 38 100 122 45 18

As shown in FIG. 57 and Table 3, when the cell gap d is made small, atthe side where the attained transmittance is near 0%, the response speedbecomes high. However, at the point where the attained transmittancebecomes 100%, the response speed does not necessarily become high. Thisis because when the cell gap d becomes small, in the case of a highapplied voltage (for example, 5 V), an electric field of excessiveintensity is applied, so that an excessive alignment occurs and it takesa time to fix the alignment direction of the liquid crystal molecules.As the cell gap d becomes small, the excessive electric field isapplied, so that the minimum point of the response speed is moved to theside of low attained transmittance. As a result of various examinationsas stated above, it has been found that in the case where the cell gap dis made small, the effect on the response speed does not simply appearby the square of the cell gap d, but the influence on the realization ofa high speed response is greater than that.

Incidentally, the material design of a liquid crystal material having anegative dielectric anisotropy is relatively difficult as compared withother liquid crystal materials. Thus, as a liquid crystal materialsatisfactorily used for a motion picture display in an active matrixtype display provided with TFTs as switching elements, the upper limitof Δn is 0.15 to 0.17.

As a result of various examinations, conditions have been found in whichthe transmittance equivalent to the prior art can be obtained, and ahigh speed response at a halftone can be realized. First, it has beenfound that in order to satisfactorily cope with a motion picturedisplay, it is appropriate that the cell gap d is 2.0 μm or less, and Δnof the liquid crystal material to be used is 0.1500 or more.

Besides, in the case of the liquid crystal cell of the ECB type such asthe MVA system, since the transmittance depends on retardation Δn·d,very large Δn·d can not be adopted. As a result of various examinations,it has been found that as the range in which the high speed response canbe realized while the characteristics of the MVA system are kept, therange in which Δn·d is from 0.30 nm to 0.42 nm is suitable.

In order to obtain the liquid crystal having the negative dielectricanisotropy and large Δn, it is effective that (1) a negative componentcompound having large Δn is introduced, or (2) a neutral materialcompound having large Δn is used.

In the case of the condition (2), it is desirable to use a liquidcrystal material having no tolan system component. If a tolan systemcompound exists, the stability and life of the liquid crystal cell arelowered. Accordingly, a liquid crystal material having no tolan systemcomponent is advantageous for an active matrix LCD required to satisfystrict electric characteristics. Thus, it is desirable to use a liquidcrystal material constituted by a liquid crystal compound containing nounsaturated bonding.

Besides, when liquid crystal molecules in the liquid crystal cell aretilted in two or more directions at the time of voltage application, theresponse characteristics and viewing angle characteristics becomeexcellent, and a multi-domain structure is desirable. In order to tiltthe liquid crystal molecules in multiple domains and in pluraldirections at the time of voltage application, it is desirable that analignment regulating structural member such as a bank or a projection isformed on a substrate surface of at least one of two oppositesubstrates, or an alignment regulating structural member of a slit-likepattern formed by partially removing a pixel electrode is formed.

In general, in the MVA-LCD, the alignment regulating structural membersuch as the bank or the projection is formed on both of the two oppositesubstrates, or the alignment regulating structural member such as thebank or the projection is formed on one of the substrates, and thealignment regulating structural member of the slit-like pattern formedby partially removing an electrode is formed on the other substrate.

With respect to the response speed, it is known that to form thealignment regulating structural member such as the bank or theprojection on both of the two opposite substrates is suitable. Also inthe liquid crystal panel of this embodiment in which the cell gap d wasmade small, in the case where the alignment regulating structural membersuch as the bank or the projection was formed on both of the twoopposite substrates, the high speed response could be most certainlyobtained.

FIG. 58 is a graph showing the relation between the height of a bank ofa liquid crystal display and the contrast ratio. The horizontal axisindicates the height (μm) of the bank, and the vertical axis indicatesthe contrast ratio. Table 4 shows the relation between the height of thebank and the contrast ratio at respective cell thicknesses of the graphof FIG. 58. Incidentally, the liquid crystal material of the MVA-LCDshown in FIG. 58 and Table 4 is liquid crystal material A having anegative dielectric anisotropy, a space width between banks of a panelhaving a cell gap d=4 μm is 25 μm, and a space width between banks of apanel having a cell gap d=2 μm is 15 μm. The width of the bank is 10 μmin both.

From FIG. 58 and Table 4, in order to keep the contrast ratio high, itis understood that the height of the bank is also important. Even if theheight of the bank is equally 1.5 μm, in the case where the cell gap dof the liquid crystal cell is large, since the influence of a taper(tilt portion) of the bank of 1.5 μm is very small, it is not concernedin light leak at the time of black display, and the contrast ratiobecomes high. In the panel having the cell gap of 4.0 μm, if the heightof the bank is 1.7 μm or less, a very high contrast ratio can be kept.On the other hand, when the cell gap d becomes 2.0 μm, the light leakbecomes high when the height of the bank is 1.5 μm. In the case wherethe cell gap d is small, since the margin region of the light leak withrespect to the height of the bank becomes small, in order to keep a highcontrast ratio, it becomes necessary to make the height of the bankequivalent to the cell gap d or less.

TABLE 4 Contrast ratio Height of bank Cell thickness = 4.0 μm Cellthickness = 2.0 μm 0.3 701 674 0.5 692 658 0.7 680 645 1.0 638 593 1.2655 380 1.4 620 212 1.7 613 181

With respect to the height of the bank of the alignment regulatingstructural member, in the conventional MVA-LCD having the cell gap d=4μm, it is 1.3 μm to 1.5 μm. If the height of the bank of the liquidcrystal panel of this embodiment having the small cell gap d is formedto be equal to the conventional bank height, the vertical alignment filmon the bank acts intensely between the opposite substrates and the lightleak in the black state occurs, so that the black level on a monitordisplay is lowered and the contrast ratio is lowered (see FIG. 58 andTable 4). Besides, when spacer dispersion or the like is considered, inorder to obtain the uniform cell gap, it is desirable that the height ofthe bank is low, and the yield in mass production is also good.Accordingly, it is desirable that the height of the bank which realizesthe high speed response and is also advantageous in mass production is1.0 μm or less.

FIGS. 59 to 61 are graphs showing the space width (pitch) dependency ofresponse characteristics of a liquid crystal display. The horizontalaxis indicates the attained transmittance (%), and the vertical axisindicates the response speed Ton (ms). FIG. 59 shows a case of the cellgap d=4 μm, FIG. 60 shows a case of the cell gap d=3 μm, and FIG. 61shows a case of the cell gap d=2 μm. Tables 5 to 7 respectively show therelation between the attained transmittance and the response speed Tonat respective space widths of the graphs of FIGS. 59 to 61. The liquidcrystal material, the bank height, and the bank width of the MVA-LCDshown in FIGS. 59 to 61 and Tables 5 to 7 are formed under the sameconditions as the MVA-LCD having the characteristics of FIGS. 55 and 56.

As is apparent from FIGS. 59 to 61 and Tables 5 to 7, when the cell gapd becomes small, since the alignment disturbance of the liquid crystaloccurs at the time of voltage application, and the response speed Ton islowered, it is necessary that the space width between adjacent alignmentregulating structural members is made smaller than 25 μm of theconventional case.

In the conventional case of the cell gap d=4.0 μm shown in FIG. 57,since the response characteristics do not have a minimum point, as shownin FIG. 59, if the space width is made small, the responsecharacteristics are directed toward the improvement as they are.

In the case where the response characteristics have a minimum point asin the case where the cell gap d is 3.0 μm or 2 μm, as shown in FIGS. 60and 61, it is effective that the space width is made small. It isconceivable that this is because the effect of the bank controlling thealignment is exerted. It is conceivable that since the liquid crystalmolecules to be aligned in the ideal direction in the plane resist theintensity of the electric field in the cell gap direction, for example,even if a voltage of 5 V is applied between the substrates at both sidesof the liquid crystal, a surplus alignment change is not produced, sothat the effect of the cell gap is exerted. It has been found that inthe case where the cell gap is 3.0 μm, the generation of a minimum pointcan be suppressed when the space width is 20 μm or less, and in the casewhere the cell gap is 2.0 μm, the generation of a minimum point can besuppressed when the space width is 15 μm or less.

Incidentally, it is not always appropriate that the space width issmall. This relates to the transmittance of the liquid crystal cell andthe contrast ratio. For example, when a voltage of 5 V is applied to theliquid crystal cell, as the transmittance becomes high, the displaybecomes bright. When the space width between the banks is made small,this transmittance becomes low. Besides, when the space width becomessmall, the bank region per unit area is increased. For example, if thenumber of banks per pixel of the LCD becomes large, light leak portionsin the black display become large, and the contrast ratio is lowered.This is because the taper portion of the bank is inclined, and theliquid crystal molecules are not aligned in the vertical direction withrespect to the substrate, so that light leaks although its amount isslight, and consequently, the contrast ratio is lowered.

That is, when the number of banks per unit area is made small, thedisplay performance is improved in both the transmittance and thecontrast ratio. However, in view of the response speed, in order toprevent a minimum point from being generated, there are conditions wherean optimum space width is obtained with respect to the cell gap.

TABLE 5 Cell Space Space Space Space thickness = width = width = width =width = 4 μm 10 μm 15 μm 20 μm 25 μm 2.5 93 150 161 180 5 68 107 116 13210 60 95 106 121 15 57 88.1 97 112 25 44 64 75 85 50 27 43 46 55 75 2128 35 38 100 17 16 17 18

TABLE 6 Cell Space Space Space Space thickness = width = width = width =width = 3 μm 10 μm 15 μm 20 μm 25 μm 2.5 68 72 88 103 5 47 50 59 72 1042 47 55 68 15 39 42 48 61 25 32 33 38 47 50 20 23 26 29 75 18 19 23 20100 17 17 19 45

TABLE 7 Cell Space Space Space Space thickness = width = width = width =width = 3 μm 10 μm 15 μm 20 μm 25 μm 2.5 33 41 47 52 5 28 32 34 36 10 2729 28 30 15 22 24 22 24 25 21 22 18 19 50 19 21 17 26 75 18 19 36 55 10017 21 70 122

FIG. 62 is a graph showing the relation between the bank width and thepanel transmittance. The horizontal axis indicates the bank width (μm),and the vertical axis indicates the panel maximum transmittance (%) atthe time of application of 5 V. Table 8 shows the relation between thebank width and the transmittance at respective cell gaps of the graph ofFIG. 62. Incidentally, the liquid crystal material of the liquid crystalpanel having a cell gap d=2 μm is after-mentioned liquid crystal C, thespace width between adjacent banks is 15 μm, and the bank height is 0.8μm. On the other hand, the liquid crystal material of the liquid crystalpanel having a cell gap d=4 μm is Liquid crystal A, the space widthbetween adjacent banks is 25 μm, and the bank height is 1.5 μm.

TABLE 8 Transmittance (%) Bank width (μm) Cell thickness = 4.0 μm Cellthickness = 2.0 μm 3 8.4 20.4 5 17.6 20.8 10 22.3 18.7 15 20.2 15.6 2014.6 13.9

When the space width between the banks becomes short, in accordance withthat, it becomes necessary to form a relatively long bank width. Whenthe bank width is small, the loss region of the transmittance becomessmall. However, the bank width also relates to the space width betweenthe banks, and in the case where the space width is large, if the bankwidth is not large to that extent, the alignment in the idealorientation can not be obtained. As in this embodiment, when the cellgap d is made small, the space width is also made small, and therefore,it becomes possible to decrease the bank width as well. As a result ofexaminations, as shown in FIG. 62 and Table 8, it has been found thatfor the stability of alignment and the prevention of luminance loss, thebank width including a manufacturing margin has only to be 3.0 μm orless.

In the case where the liquid crystal panel having a small cell gap d isfabricated, in a conventional fabrication method (vacuum dip injectionmethod), an injection time becomes long, and from a problem of tact,eventually, the manufacturing cost is raised. Then, in the manufactureof the liquid crystal display according this embodiment, a droppinginjection method is used. The dropping injection method has a merit inthat the injection time can be shortened, and especially, a liquidcrystal display having an enlarged size and a narrowed space greatlyreceives benefit of the merit.

Further, a liquid crystal material containing a liquid crystal compound,which is suitable for the dropping injection method and has highvolatility in vacuum, can be used, and by the introduction of the liquidcrystal compound, the rotational viscosity (γ1) of the liquid crystalmaterial having the negative dielectric anisotropy can be made small andthe response speed can be improved.

With respect to the liquid crystal compound having high volatility invacuum, since the composition ratio of the liquid crystal material ischanged by volatilization in the conventional vacuum dip injectionprocess of the TN type LCD, the compound is judged to be unsuitable formass production and is not in use. However, although a time in which theliquid crystal is put in vacuum is as long as about 6 to 7 hours in thevacuum dip injection process, it is about one minute in the droppinginjection step, which is an extraordinary short time. Thus, it becomespossible to use the liquid crystal compound having volatility in vacuum,which is rather higher than that conventionally used, for massproduction. As a result of examinations, it has been confirmed that whenthe material having high volatility is used, the rotational viscosity γ1of the liquid crystal can be lowered by 20 to 30 percent, and this alsocontributes to the improvement of the response speed of the liquidcrystal cell.

It is known that in general, when Δn of the liquid crystal materialbecomes high, the wavelength dependency of Δn becomes high. This meansthat in the liquid crystal panel, the wavelength dependency becomes highin the voltage-transmittance characteristics as well. Even in the liquidcrystal panel in which high speed can be realized, if the wavelengthdependency is high, there is a case where coloring occurs by atransmission spectrum, and chromaticity characteristics are lowered.Especially, when a refractive index anisotropy in the blue wavelengthregion becomes high and the wavelength dependency ofvoltage-transmittance characteristics of blue becomes high, as comparedwith green or red, a color shift becomes noticeable. As a method ofcorrecting the color shift, a space width between a structural memberand a structural member in the pixel is changed, and a structural memberpattern may be adopted in which the space width becomes large in orderof blue, green and red. Since the blue wavelength region issubstantially prominent, when the space portion pitch in only the blueportion is made smaller than that of green or red, the chromaticitycharacteristics are greatly improved.

Hereinafter, specific examples will be described.

EXAMPLE 1

Resist S1808 (made by Shipley) was patterned and thermally hardened toform banks (width of 3 μm) on a substrate having an ITO electrode. Afterthis substrate was subjected to an ashing processing, an alignment filmusing vertical alignment film material X was formed by a spinner. Theheight of the bank was made 0.7 μm. Predetermined spacers were scatteredon one of the substrates, and the substrates were bonded to each otherby using a thermosetting seal material, so that empty cells werefabricated (spacer: 2.0 μm, 3.0 μm, 4.0 μm). When the substrates werebonded to each other, the intervals (alignment control) between banksand slit portions are 5 μm, 10 μm, and 15 μm. Liquid crystal material A,liquid crystal B, liquid crystal C and liquid crystal D, which weredifferent from each other in viscosity·Δn, were respectively injected tothese empty cells and were sealed, and polarizing plates were bonded incrossed Nicols, so that MVA cells were fabricated. The cell gap wasobtained by a cell thickness measurement device of Oak Seisakusho Co.,Ltd. The combinations of the liquid crystal B, the liquid crystal C, theliquid crystal D and the cell gap are made such that Δn·d values becomeequal to each other.

Here, Table 9 shows characteristics of the liquid crystals A, B, C andD.

TABLE 9 Physical property values of liquid crystal materials LiquidLiquid Liquid Liquid crystal A crystal B crystal C crystal D NI point71° C. 70° C. 90° C. 70° C. Δn 0.0822 0.1321 0.1535 0.1669 Δε −3.8 −3.8−5.0 −4.1 K₁₁ 13.6 11.3 14.7 12.6 K₃₃ 14.7 14.7 21.0 17.7 γ1 135 187 320234

T-V characteristics of the respective MVA cells were measured, a voltageof 5.4 V causing an actual white display was made 100%, and responsetimes from 0% to 25%, 50%, and 100% were measured. As a result, it hasbeen found that as compared with the case where the cell gap is large(4.0 μm), as the cell gap becomes small, the speed becomes highespecially in the halftone region. In the case where the cell gap issmall, the dependency on liquid crystal viscosity becomes low, andrestriction to the liquid crystal material used for the MVA cell isrelaxed.

Since an alignment blur occurs at the time of high voltage applicationwhen the space pitch between a bank portion and a bank portion exceeds15 μm, it has been found that the space pitch is desirably 15 μm orless. When the space pitch is less than 15 μm, since the transmittanceat the time of voltage application in the T-V characteristics islowered, it is desirable that the space pitch is made 15 μm.

When the width of the bank portion was 3 μm or more, the transmittancewas lowered as well, and a desirable tendency was not obtained. In thecase where the height of the bank was 1.0 μm or more, since thetransmittance at the time of no voltage application was high, and thelight leak occurred, the contrast ratio became small, and an excellentresult was not obtained.

As described above, according to the liquid crystal display of thisembodiment, the response speed can be made high, and especially,“persistence of vision” and “display blur” which are the problem in thehalftone display can be relieved, and the display performance of theMVA-LCD can be improved.

Ninth Embodiment

Next, an LCD according to a ninth embodiment of the present inventionwill be described with reference to FIGS. 63 to 72D. This embodimentrelates to panel construction conditions of the LCD, and especiallyrelates to the improvement of the response speed of the VA system LCDusing a liquid crystal having a negative dielectric anisotropy.

Since the VA system LCD using the liquid crystal having the negativedielectric anisotropy has a high contrast and excellent responsecharacteristics, various systems have been developed. Especially, theMVA-LCD using multiple domains is excellent in viewing anglecharacteristics, and is mass-produced as a high performance liquidcrystal monitor.

With the advancement of multimedia in recent years, the demand for amotion picture monitor from a still picture monitor has been raised, anLCD which completes a response in one frame (16.7 ms) has been required.The improvement of the response characteristics of the TN type and theIPS type have been advanced, and also in the MVA-LCD, the improvement ofthe response characteristics is desired.

FIG. 63 explains a problem to be solved by this embodiment, and showsthe response characteristics of an MVA-LCD at respective halftone levelsbefore switching. The horizontal axis indicates the halftone level afterswitching, and the vertical axis indicates the response time (ms)required before and after switching. Here, the definition of a halftoneis illustrated in FIG. 64. FIG. 64 shows the luminance of transmittedlight with respect to the applied voltage in the MVA-LCD, and showsrespective halftone levels. The horizontal axis indicates the appliedvoltage (V), and the vertical axis indicates the luminance oftransmitted light (a.u.). As shown in FIG. 63, when a complete whitedisplay (halftone level 8) is obtained, the response time is shortirrespective of the halftone level before the switching. However, when ahalftone display is obtained, since a response time of several tens msor longer is required, persistence of vision, display blur or the likeis caused on a monitor screen. Especially, when the switching isperformed from the halftone level 0 to a low halftone level such as thehalftone levels 1 and 2, a long response time is required.

Besides, FIG. 65 explains a problem to be solved by this embodiment, andshows the response characteristics of a VA system LCD at respectivehalftone levels before switching. Similarly to FIG. 63, the horizontalaxis indicates the halftone level after the switching, and the verticalaxis indicates the response time (ms). As shown in FIG. 65, when acomplete white display (halftone level 8) is obtained, the response timeis short irrespective of the halftone level before the switching.However, when a halftone display is obtained, since a response time ofseveral tens ms or longer is required, persistence of vision, displayblur or the like is caused on a monitor screen. Especially, when theswitching is performed from the halftone level 0 to a low halftone levelsuch as the halftone levels 1 and 2, a long response time is required.

The response characteristics of the VA system LCD using the liquidcrystal having the negative dielectric anisotropy depends on parameterssuch as rotational viscosity γ₁ of a liquid crystal material, elasticconstant K₁₁ of a spray, elastic constant K₃₃ of a bend, and dielectricanisotropy Δ∈. However, since these parameters have correlations betweenthem, it is difficult to optimize all the parameters.

The VA system LCD using the liquid crystal having the negativedielectric anisotropy has response characteristics capable of respondingin one frame at all gradations when rotational viscosity γ₁ (unit ismPa·s) of a liquid crystal material, elastic constant K₁₁ (unit is pN)of a spray, elastic constant K₃₃ (unit is pN) of a bend, dielectricanisotropy Δ∈, and a cell gap d (unit is μm) satisfy(γ₁−1.1)×(K ₁₁+233.7)×(K₃₃+36.9)×(d−1.1)×(Δ∈⁴+31.7Δ∈³+370.8Δ∈²+1948.6Δ∈+4304.2)≦8.8×10⁸.  (expression3)

Besides, the MVA-LCD in which the liquid crystal having the negativedielectric anisotropy is sandwiched between two substrates each having asurface subjected to a vertical alignment processing, and an alignmentregulating structural member is formed on at least one substratesurface, has response characteristics capable of responding in one frameat all gradations when rotational viscosity γ₁ (unit is mPa·s) of aliquid crystal material, elastic constant K₁₁ (unit is pN) of a spray,elastic constant K₃₃ (unit is pN) of a bend, dielectric anisotropy Δ∈,and a cell gap d (unit is μm) satisfy(γ₁−1.1)×(K ₁₁+875.6)×(K ₃₃+50.6)×(d ⁴+2.7d ³+9.5d²+430.8d+524.1)×(Δ∈⁴+31.7Δ∈³+370.8Δ∈²+1948.6Δ∈+4304.2)≦1.6×10¹².  (expression4)

Hereinafter, specific examples will be described.

EXAMPLE 9-1

With respect to the response time of a VA system LCD, the dependency onrotational viscosity γ₁ of a liquid crystal material, elastic constantK₁₁ of a spray, elastic constant K₃₃ of a bend, dielectric anisotropyΔ∈, and a liquid crystal layer thickness d was simulated. FIG. 66 showsparameter dependency of an on state response time in the VA system LCD.The horizontal axis indicates the parameter variation (%), and thevertical axis indicates the on state response time variation Δt(%). Asreference values of γ₁, K₁₁, K₃₃, Δ∈ and d, typical values of a liquidcrystal material having a negative dielectric anisotropy shown in Table10 were used.

TABLE 10 γ₁ 150 mPa · s K₁₁ 12 pN K₃₃ 12 pN Δε −3 d 4 μm

As shown in FIG. 66, the degrees of influence of the respectiveparameters on the response characteristics are greatly different fromone another. Besides, as shown in FIG. 65, under the conditions shown inTable 10, the response time from the halftone level 0 to the halftonelevel 1, which requires the longest time in the response characteristicsof the VA system LCD, was 69.5 ms.

A variation of the response time in the on state by γ₁ is made Δt(γ₁). Avariation of the response time in the on state by K₁₁ is made Δt(K₁₁),and a variation of the response time in the on state by K₃₃ is madeΔt(K₃₃). Besides, a variation of the response time in the on state by Δ∈is made Δt(Δ∈), and a variation of the response time in the on state byd is made Δt(d). When the least square method is used for the resultsobtained in FIG. 66, Δt(γ₁), Δt(K₁₁), Δt(K₃₃), Δt(Δ∈), and Δt(d) arerespectively expressed as follows:Δt(γ₁)=7.4667×10⁻³γ₁−1.008  (expression 5)Δt(K ₁₁)=4.044×10⁻³ K ₁₁−0.055  (expression 6)Δt(K ₃₃)=1.938×10⁻² K ₃₃−0.285  (expression 7)Δt(Δ∈)=1.3826×10⁻³Δ∈⁴+4.3821×10⁻²Δ∈³+51.2690×10⁻²Δ∈²+2.6942Δ∈+4.9511  (expression8)Δt(d)=0.339d−1.354  (expression 9)

If the response time from the halftone level 0 to the halftone level 1,which is the slowest response time, is 16.7 ms or less, a response inone frame can be realized at all gradations. When the response timevariation by all the parameters is considered, a variation f of theresponse time in the VA system LCD when γ₁, K₁₁, K₃₃, Δ∈ and d arechanged is expressed as follows:f=[1+Δt(γ₁)]·[1+Δt(K ₁₁)]·[1+Δt(K ₃₃)]·[1+Δt(Δ∈)]·[1+Δt(d)]  (expression10)

Since the response time from the halftone level 0 to the halftone level1, which is the slowest response time, is 69.5 ms, in order to make this16.7 ms or less, the following condition must be satisfied.

[Mathematical Formula 1]f≦1−(69.5−16.7)/69.5  (expression 11)

When the expressions (5) to (10) are substituted for the expression(11), the following expression is obtained.(γ₁−1.1)×(K ₁₁+233.7)×(K₃₃+36.9)×(d−1.1)×(Δ∈⁴+31.7Δ∈³+370.8Δ∈²+1948.6Δ∈+4304.2)≦8.8×10⁸  (expression12)

EXAMPLE 9-2

A VA system LCD was fabricated by using a liquid crystal material shownin Table 11. As an alignment film, a vertical alignment film material Xwas used, and rubbing was performed six times (extrusion amount of 0.2mm) with nylon. Table 11 shows parameters of the liquid crystalmaterial. In any of liquid crystals 1 to 5 shown in Table 11, theexpression (12) is established.

TABLE 11 Liquid Liquid Liquid Liquid Liquid crystal 1 crystal 2 crystal3 crystal 4 crystal 5 γ₁ (mPa · s) 178 135 99 99 72 K₁₁ (pN) 13.0 13.610.7 7.9 8.8 K₃₃ (pN) 14.9 14.7 12.9 9.6 10.5 Δε −3.7 −3.8 −3.4 −2.3−2.9 d (μm) 1.6 1.7 2.0 1.5 2.0

FIG. 67 shows results obtained when the response characteristics in theon state are measured. FIG. 67 shows the response characteristics of theVA system LCD using the liquid crystals 1 to 5 shown in Table 11 forevery liquid crystal material. The horizontal axis indicates thetransmittance (%) after switching, and the vertical axis indicates theresponse time (ms). Here, the transmittance before switching (blackdisplay state at an applied voltage of 0 V) is made 0%, and thetransmittance when the applied voltage is 5 V is made 100%. As shown inFIG. 67, in any cases, the response characteristics of 16.7 ms or lessare realized, and the validity of the expression (12) can be confirmed.

In the liquid crystal materials shown in Table 11, in order to improvethe response characteristics, the respective parameters are assumed tobe realistic. In the liquid crystal 1, a case where the rotationalviscosity γ₁ is large is assumed, and the cell gap d is made small sothat the response characteristics are improved. In the liquid crystal 2,the dielectric anisotropy Δ∈ is made large so that the responsecharacteristics are improved. In the liquid crystal 3, the rotationalviscosity γ₁ is made small so that the response characteristics areimproved. In the liquid crystal 4, if γ₁ is made small in an actualliquid crystal material, the elastic constants K₁₁, K₃₃ and Δ∈ tend todecrease, and accordingly, the cell gap d is made small so that theresponse characteristics are improved. In the liquid crystal 5, γ₁ ismade smaller than that of the liquid crystal 3 so that the responsecharacteristics are improved.

EXAMPLE 9-3

FIG. 68 shows a sectional construction of an MVA-LCD. A liquid crystallayer 3 is sealed between two glass substrates 1 and 2 which have apredetermined cell gap d and are bonded opposite to each other.Transparent electrodes 11 and 12 made of ITO are respectively formed onopposite surfaces of the two opposite substrates 1 and 2. Besides,polarizing plates 30 arranged in crossed Nicols are formed on outsidesurfaces of both the substrates. A plurality of linear projections 4 areformed on the transparent electrode 11 of the substrate 1. On the otherhand, a plurality of linear projections 6 arranged at the same pitch asthe linear projections 4 and shifted from the linear projections 4 by ahalf pitch are formed on the transparent electrode 12 of the substrate2. Each of the linear projections 4 and 6 is formed to have a width wand a height h. The linear projections 4 and the linear projections 6have spaces s in a substrate surface direction.

FIG. 69 shows a propagation state of tilts of liquid crystal moleculesin the MVA-LCD. As shown in FIG. 69, since the tilt of the liquidcrystal molecule in the vicinity of the linear projection 6 in apredetermined orientation is successively propagated to the space sbetween the linear projections 4 and 6 shown in FIG. 68, the MVA-LCD hasresponse characteristics different from the VA system.

With respect to the response time of the MVA-LCD shown in FIG. 68, thedependency on rotational viscosity γ₁ of a liquid crystal material,elastic constant K₁₁ of a spray, elastic constant K₃₃ of a bend,dielectric anisotropy Δ∈, and a cell gap d was simulated. Here, thespaces between the linear projections 4 and 6 is set to 25 μm, theheight h is set to 1 μm, and the width w is set to 5 μm, respectively,and the liquid crystal material shown in Table 10 is used as thestandard. FIG. 70 shows the parameter dependency of the on stateresponse time in the MVA-LCD. As shown in FIG. 70, the degrees ofinfluence of the respective parameters on the response characteristicsare greatly different from one another. Besides, as shown in FIG. 63,under the conditions shown in Table 10, the response time from thehalftone level 0 to the halftone level 1, which required the longesttime in the response characteristics of the MVA-LCD, was 91.5 ms.

A variation of the response time in the on state by γ₁ is made Δt′(γ₁).A variation of the response time in the on state by K₁₁ is madeΔt′(K₁₁), and a variation of the response time in the on state by K₃₃ ismade Δt′(K₃₃). Besides, a variation of the response time in the on stateby Δ∈ is made Δt′(Δ∈), and a variation of the response time in the onstate by d is made Δt′(d). When the least square method is used for theresults obtained in FIG. 70, Δt′(γ₁), Δt′(K₁₁), Δt′(K₃₃), Δt′(Δ∈) andΔt′(d) are respectively expressed as follows:Δt′(γ₁)=7.4667×10⁻³γ₁−1.008  (expression 13)Δt′(K ₁₁)=1.125×10⁻³ K ₁₁−0.015  (expression 14)Δt′(K ₃₃)=1.531×10⁻² K ₃₃−0.225  (expression 15)Δt′(Δ∈)=1.3826×10⁻³Δ∈⁴+4.3821×10⁻²Δ∈³+51.2690×10⁻²Δ∈²+2.6942Δ∈+4.9511  (expression16)Δt′(d)=6.5120×10⁻⁴ d ⁴+1.7511×10⁻³ d ³+6.2138×10⁻³ d²+0.28053d−0.65873  (expression 17)

In order to realize a response in one frame at all gradations, if theresponse time from the halftone level 0 to the halftone level 1, whichis the slowest response time, is 16.7 ms or less, the response in oneframe can be realized at all gradations. When the variation of theresponse time by all the parameters is considered, a variation f′ of theresponse time of the MVA-LCD when γ₁, K₁₁, K₃₃, Δ∈ and d are changed isexpressed as follows:f′=[1+Δt′(γ₁)]·[1+Δt′(K ₁₁)]·[1+Δt′(K₃₃)]·[1+Δt′(Δ∈)]·[1+Δt′(Δd)]  (expression 18)

Since the response time from the halftone level 0 to the halftone level1, which is the slowest response time, is 91.5 ms, in order to make this16.7 ms or less, the following condition has only to be satisfied.

[Mathematical Formula 2]f′≦1−(91.5−16.7)/91.5  (expression 19)

When the expressions (13) to (18) are substituted for the expression(19), the following expression is obtained.(γ₁−1.1)×(K ₁₁+875.6)×(K ₃₃+50.6)×(d ⁴+2.7d ³+9.5d²+430.8d+524.1)×(Δ∈⁴+31.7Δ∈³+370.8Δ∈²+1948.6Δ∈+4304.2)≦1.6×10¹²  (expression20)

EXAMPLE 9-4

FIG. 71 shows a sectional construction of an MVA-LCD according to thisexample. As shown in FIG. 71, in the MVA-LCD according to this example,instead of the linear projections 6 shown in FIG. 68, slits 8 are formedon the glass substrate 2. Besides, in addition to the combination of thelinear projections 4 and the slits 8, even if the slits 8 are formed onboth the glass substrates 1 and 2, the MVA-LCD can be realized.

EXAMPLE 9-5

A vertical alignment film material X was used for alignment films 11 and12, and resist LC-200 of Shipley was used for linear projections 4 and6, so that an MVA-LCD was fabricated. Each of the linear projections 4and 6 was formed to have a width of 5 μm and a height of 1 μm. Liquidcrystal material A having a negative dielectric anisotropy was used asthe liquid crystal material. FIGS. 72A to 72D show results of amicroscopic observation of transient response characteristics of theMVA-LCD in which the space s is changed. FIG. 72A shows the result whenthe space s is 6 μm, and FIG. 72B shows the result when the space s is15 μm. FIG. 72C shows the result when the space s is 30 μm, and FIG. 72Dshows the result when the space s is 45 μm. Applied voltage was made 5 Vfor the respective cases. As shown in FIGS. 72A to 72D, when the space sbecomes 30 μm or more, a uniform alignment can not be obtained.

Table 12 and Table 13 show the relation between the space s and thealignment state of liquid crystal in this example. Table 12 shows thealignment states when the space s is 15 μm or less, and Table 13 showsthe alignment states when the space s is 20 μm or more. In the tables,the alignment states are denoted by O, Δ and x. The symbol O denotesthat a uniform alignment is obtained, and Δ denotes that a uniformalignment is obtained though several domains are generated. The symbol xdenotes that a number of domains are generated and a uniform alignmentis not obtained.

TABLE 12 Space s (μm) 5 6 7.5 10 12.5 15 Alignment ∘ ∘ ∘ ∘ ∘ ∘ state

TABLE 13 Space s (μm) 20 25 30 40 50 75 Alignment ∘ Δ x x x x state

As shown in Table 12 and Table 13, if the space s is 25 μm or less, theuniform alignment is obtained. On the other hand, if the space s islarger than 25 μm, a number of domains are generated in the spaceportion, and the uniform alignment is not obtained.

When the space s is 25 μm or less, as shown in FIG. 69, since the tiltin a predetermined orientation is successively propagated from thelinear projection 6, the uniform alignment is obtained. On the otherhand, when the space s is larger than 25 μm, there is a region which istilted in a different orientation before the tilt is propagated from thelinear projection 6. Thus, a number of domains are generated and theuniform alignment is not obtained. Accordingly, in the MVA-LCD, it isnecessary that the space s is made 25 μm or less.

EXAMPLE 9-6

In order to improve viewing angle characteristics, it is also possibleto provide an optical compensation layer as optical compensation meansbetween a polarizing plate and a glass substrate. As the opticalcompensation layer, a uniaxial or biaxial phase difference film can beused.

As described above, in the liquid crystal display according to thisembodiment, the response speed can be made high, and persistence ofvision, display blur or the like, which becomes a problem in display,can be relieved, and this embodiment can contribute to the improvementof display performance of the VA type liquid crystal display.

As described above, according to the present invention, it is possibleto suppress the drop in the transmittance and to improve the responsecharacteristics. Besides, according to the present invention, it ispossible to suppress the deterioration of the response characteristicsand to improve the transmittance.

1. A liquid crystal display comprising: a pair of substrates arrangedopposite to each other; electrodes respectively formed on oppositesurfaces of the pair of substrates; an alignment regulating structuralmember which includes at least one of a linear projection arranged onthe electrode and a slit portion formed by removing a part of anelectrode material of the electrode, and is formed on at least one ofthe pair of substrates; and a liquid crystal layer sealed between thesubstrates and having a negative dielectric anisotropy, in whichalignment control is made such that when a voltage is applied to theelectrodes, an alignment orientation of a liquid crystal domain in aregion adjacent to the alignment regulating structural member isdifferent from an extending direction of the alignment regulatingstructural member by approximately 45°, and at a time of no voltageapplication, a liquid crystal molecule of a region where the alignmentregulating structural member does not exist is substantially verticallyaligned, and a liquid crystal molecule on the alignment regulatingstructural member or on its opposite portion is un-vertically aligned.2. A liquid crystal display according to claim 1, wherein a pre-tiltangle of the liquid crystal molecule on the alignment regulatingstructural member at the time of no voltage application is approximately0°.
 3. A liquid crystal display according to claim 1, wherein analignment film at the alignment regulating structural member or at theopposite portion is thinner than the film in a region where thealignment regulating structural member does not exist.
 4. A liquidcrystal display according to claim 3, wherein the alignment film is notformed at the alignment regulating structural member or the oppositeportion.
 5. A liquid crystal display according to claim 1, wherein aheight of a partial region of the linear projection is changed.
 6. Aliquid crystal display according to claim 1, wherein a width of thealignment regulating structural member orthogonal to an extendingdirection of the alignment regulating structural member is changed.
 7. Aliquid crystal display according to claim 1, wherein a structural memberhaving directionality in a substrate surface direction is arranged atleast one of the alignment regulating structural member or the oppositeportion.